Help with functions and general advice

I'm not totally new to powershell, it's just that my scripts have been getting more complex and some concepts elude me.  My scripts seem overly long because I use a lot of functions with repeatable pieces.  It seems like I could do variables somewhere in my functions but I really don't understand where to start (and I've been searching).

This script formats and labels disks based on the number of disks added to a Windows virtual machine (2k8r2).  I use a lot of functions (and the script works...which is usually where I stop)... it's just that I'm just trying to improve my scripting abilities.  So the big question is how do I shorten this up?  Is there a better way to lay out and write my code?  Any advice would be appreciated.  Thanks

#Powershell script to pull info from diskpart and format disks
#Date      : 09/15/2014

Function DISKFORMAT
{NEW-ITEM -Name detail.txt -ItemType file -force | OUT-NULL
ADD-CONTENT -Path detail.txt "SELECT DISK $DISKID"
ADD-CONTENT -Path detail.txt "CREATE PARTITION PRIMARY"
ADD-CONTENT -Path detail.txt "FORMAT FS=NTFS QUICK"
ADD-CONTENT -Path detail.txt "ASSIGN"
$DETAIL=(DISKPART /S detail.txt)}

Function SQLDIR1
{New-Item -Path D:\MSSQL -ItemType directory
New-Item -Path D:\MSSQL\DATA01 -ItemType directory
New-Item -Path D:\MSSQL\TRANS01 -ItemType directory
New-Item -Path D:\MSSQL\LOG01 -ItemType directory
New-Item -Path D:\MSSQL\TEMPDB -ItemType directory}

Function SQLDIR2
{New-Item -Path D:\MSSQL -ItemType directory
New-Item -Path D:\MSSQL\DATA01 -ItemType directory
New-Item -Path D:\MSSQL\TRANS01 -ItemType directory
New-Item -Path D:\MSSQL\LOG01 -ItemType directory
New-Item -Path D:\MSSQL\TEMPDB -ItemType directory
New-Item -Path D:\MSSQL\Backup -ItemType directory}

Function SQLDATA01
{NEW-ITEM -Name detail.txt -ItemType file -force | OUT-NULL
ADD-CONTENT -Path detail.txt "SELECT DISK $DISKID"
ADD-CONTENT -Path detail.txt "CREATE PARTITION PRIMARY"
ADD-CONTENT -Path detail.txt "FORMAT FS=NTFS UNIT=64K QUICK"
ADD-CONTENT -Path detail.txt "ASSIGN MOUNT=D:\MSSQL\DATA01"}

Function SQLTRANS01
{NEW-ITEM -Name detail.txt -ItemType file -force | OUT-NULL
ADD-CONTENT -Path detail.txt "SELECT DISK $DISKID"
ADD-CONTENT -Path detail.txt "CREATE PARTITION PRIMARY"
ADD-CONTENT -Path detail.txt "FORMAT FS=NTFS UNIT=64K QUICK"
ADD-CONTENT -Path detail.txt "ASSIGN MOUNT=D:\MSSQL\TRANS01"}

Function SQLLOG01
{NEW-ITEM -Name detail.txt -ItemType file -force | OUT-NULL
ADD-CONTENT -Path detail.txt "SELECT DISK $DISKID"
ADD-CONTENT -Path detail.txt "CREATE PARTITION PRIMARY"
ADD-CONTENT -Path detail.txt "FORMAT FS=NTFS UNIT=64K QUICK"
ADD-CONTENT -Path detail.txt "ASSIGN MOUNT=D:\MSSQL\LOG01"}

Function SQLTEMPDB
{NEW-ITEM -Name detail.txt -ItemType file -force | OUT-NULL
ADD-CONTENT -Path detail.txt "SELECT DISK $DISKID"
ADD-CONTENT -Path detail.txt "CREATE PARTITION PRIMARY"
ADD-CONTENT -Path detail.txt "FORMAT FS=NTFS UNIT=64K QUICK"
ADD-CONTENT -Path detail.txt "ASSIGN MOUNT=D:\MSSQL\TEMPDB"}

Function SQLBACKUP
{NEW-ITEM -Name detail.txt -ItemType file -force | OUT-NULL
ADD-CONTENT -Path detail.txt "SELECT DISK $DISKID"
ADD-CONTENT -Path detail.txt "CREATE PARTITION PRIMARY"
ADD-CONTENT -Path detail.txt "FORMAT FS=NTFS UNIT=64K QUICK"
ADD-CONTENT -Path detail.txt "ASSIGN MOUNT=D:\MSSQL\Backup"}

Function LABEL1
{$drive = Get-WmiObject -Class win32_volume -Filter "DriveLetter = 'C:'"
    Set-WmiInstance -input $drive -Arguments @{DriveLetter="C:"; Label="OS"}}

Function LABEL2
{$drive = Get-WmiObject -Class win32_volume -Filter "DriveLetter = 'C:'"
    Set-WmiInstance -input $drive -Arguments @{DriveLetter="C:"; Label="OS"}
$drive = Get-WmiObject -Class win32_volume -Filter "DriveLetter = 'D:'"
    Set-WmiInstance -input $drive -Arguments @{DriveLetter="D:"; Label="Data"}}

Function LABEL3
{$drive = Get-WmiObject -Class win32_volume -Filter "DriveLetter = 'C:'"
    Set-WmiInstance -input $drive -Arguments @{DriveLetter="C:"; Label="OS"}
$drive = Get-WmiObject -Class win32_volume -Filter "DriveLetter = 'D:'"
    Set-WmiInstance -input $drive -Arguments @{DriveLetter="D:"; Label="Apps"}
$drive = Get-WmiObject -Class win32_volume -Filter "DriveLetter = 'E:'"
    Set-WmiInstance -input $drive -Arguments @{DriveLetter="E:"; Label="Data"}}
    
Function LABEL4
{$drive = Get-WmiObject -Class win32_volume -Filter "DriveLetter = 'C:'"
    Set-WmiInstance -input $drive -Arguments @{DriveLetter="C:"; Label="OS"}
$drive = Get-WmiObject -Class win32_volume -Filter "DriveLetter = 'D:'"
    Set-WmiInstance -input $drive -Arguments @{DriveLetter="D:"; Label="Apps"}
$drive = Get-WmiObject -Class win32_volume -Filter "DriveLetter = 'E:'"
    Set-WmiInstance -input $drive -Arguments @{DriveLetter="E:"; Label="Data"}
$drive = Get-WmiObject -Class win32_volume -Filter "DriveLetter = 'F:'"
    Set-WmiInstance -input $drive -Arguments @{DriveLetter="F:"; Label="Data01"}}

# List All disks
NEW-ITEM –name listdisk.txt –itemtype file –force | OUT-NULL
ADD-CONTENT –path listdisk.txt "LIST DISK"
$LISTDISK=(DISKPART /S listdisk.txt)
$TOTALDISK=($LISTDISK.Count)-7

#If there's only one disk (OS DISK) Exit the script
IF ($TOTALDISK -eq 1)
{LABEL1}

IF ($TOTALDISK -eq 2)
{$DISKID=$LISTDISK[8].substring(7,5).trim()
DISKFORMAT 
LABEL2}

IF ($TOTALDISK -eq 3) 
{$DISKID=$LISTDISK[8].substring(7,5).trim()
DISKFORMAT
$DISKID=$LISTDISK[9].substring(7,5).trim()
DISKFORMAT 
LABEL3}

IF ($TOTALDISK -eq 4) 
{$DISKID=$LISTDISK[8].substring(7,5).trim()
DISKFORMAT
$DISKID=$LISTDISK[9].substring(7,5).trim()
DISKFORMAT
$DISKID=$LISTDISK[10].substring(7,5).trim()
DISKFORMAT
LABEL4}

IF ($TOTALDISK -eq 5) 
{$DISKID=$LISTDISK[8].substring(7,5).trim()
DISKFORMAT 
LABEL2
SQLDIR1
SQLDATA01
SQLTRANS01
SQLLOG01
SQLTEMPDB}

IF ($TOTALDISK -eq 6) 
{$DISKID=$LISTDISK[8].substring(7,5).trim()
DISKFORMAT 
LABEL2
SQLDIR2
SQLDATA01
SQLTRANS01
SQLLOG01
SQLTEMPDB
SQLBACKUP}


ELSE {EXIT}