Is yours a 2.2 (NA) or 2.0 (Turbo)?

Changing the speakers on both is pretty easy - the hardest part is getting to the passenger-side one, as the seat isn't adjustable.

Standard 17cm speakers will fit in both cars, but the mounting depth needs to be less than 65mm, which limits the choice somewhat. There are still a bunch of options available though. Coaxials are far easier to fit, as you don't have to run wiring to the front of the car for tweeters, but drag the soundstage back even further.

Removing the old speakers is pretty easy - on the turbo there are four visible screws on the grilles, just remove these and out the speaker comes. On the NA, the screws are hidden behind the grilles, so you need to remove them - you'll need something to lever them out, but be aware that you're levering the grill out from the round plastic surround, NOT the plastic surround from the car panel.

There's loads more info on the vx220.org.uk forums, worth checking if you haven't looked already.

Let me know if you have any more questions.