To turn Airport on or off, use:

do shell script "networksetup -setairportpower en1 on"

as described here and in this Macworld hint in the comments. You might need to change en1 if your Airport adapter is named differently (unlikely).

Another blogpost suggests to use the Macports utility 'airport' to do this, which seems more cumbersome. Also, there are various elaborate alternatives which seem extremely unstable.

To change your Time Machine backup disk, macworld.com has a hint on how to do this properly. You need to manually connect each disk first and salvage /Library/Preferences/com.apple.TimeMachine.plist for all disks. Then you can use a script to automatically change this file when necessary. The script is as follows (with changes as suggested in the comments).

-- Change Time Machine backup to available disk
-- From http://lifehacker.com/5543791/back-up-your-mac-to-multiple-disks-with-time-machine
property pth : (path to preferences folder from local domain) as text
property d1name : "TimeMachine @ home"
property d1 : "com.apple.TimeMachine.home.plist"
property d2name : "TimeMachine @ work"
property d2 : "com.apple.TimeMachine.work.plist"
property active : "com.apple.TimeMachine.plist"

do shell script "defaults write com.apple.TimeMachine AutoBackup -bool false"

-- TvW: Changed script slightly, simply overwrite the defaults with the cached settings here
if (list disks) contains d1name then
        tell application "Finder" to if exists (pth & d1) then
                if exists (pth & active) then
                        delete (pth & active)
                end if
                set theCopy to duplicate file (pth & d1)
                set the name of theCopy to active
        end if
else if (list disks) contains d2name then
        tell application "Finder" to if exists (pth & d2) then
                if exists (pth & active) then
                        delete (pth & active)
                end if
                set theCopy to duplicate file (pth & d2)
                set the name of theCopy to active
        end if
end if

do shell script "defaults write com.apple.TimeMachine AutoBackup -bool true"
-- Run backup immediately
do shell script "/System/Library/CoreServices/backupd.bundle/Contents/Resources/backupd-helper > /dev/null 2>&1 &"