Sounds like a great list you have there Wagits,

Suspension should be first, or you'll wreck your new tyres. There are heaps and heaps of 17's that will fit 4x100 golfs. Most sets can be had for very close to $1000 including budget low profile tyres. Have a look at www.tempetyres.com.au for pricing purposes.

There is no sound deadening under the bonnet.

The headliner is an easy mod, many on here have done it. I took mine out altogether because I have a 7inch monitor up there.

I changed my GL seats for Vr6 ones, which several people on here have also done. You can get your existing steering wheel covered in leather by a motor trimmer for pretty cheap too.

Most of the mods you listed have been done several times by a lot of the super friendly MK3 guys on here. So just do a search or check out previous threads. Better to do it nice, than do it twice.

One last thing...Best mod for a 2.0 MK3, is a VR6 front lip. $80ish bucks adds all the tough!

Good Luck