If you want to D.I.Y or make it easy the car and the highline both need to be pre 2006.
Thats highline part numbers ending in 970,971,972 and current midline ending in 960,961 and 962. These part numbers are interchangable you can fit a 971 in a 962 car likewise a 972 in a 960 car ect. You can fit later/new highlines but you will need to go to the dealer or specialist to get this done at a cost of around £350-£400. If you want to D.I.Y then you can pick them up second hand for between £40-£200. Although if you choose this option then you'll need or find someone with the right software
aswell as VCDS to do the swap (unless you manage to find a highline which is supplied with the security code).Darren(Mortygttdi) Eddie (EddieNL) and I all have this software aswell as others.
For the multifunction wheel then you'll need a new controller and airbag loom and possibly slip ring although if the car has a midline display as oppose to a lowline display you should have the correct one (slip ring). New controller around £130 from the dealers to £40-£80 second hand, Loom £35 from the dealers around £20 secondhand.Again you'll need VCDS or someone with it to code it for you.
Also just to add if you use a highline ending in 972 then the MFSW will need to be the later model with the menu button. If its 970,971 then the older MFSW will be needed.
The dash insert part number is 1K0 920 followed by the three numbers mentioned above.