Hi and welcome to Golf ownership

If you have ever owned an Audi/BMW/Mercedes you will be rightly dismissive of dealer prices. However, your local VW dealer can be surprisingly cost effective for parts. Especially body parts as you know these will fit. Also service consumables.
Don't discount the scrappy either. The Mk3 is starting to get rare but there should still be a good choice of parts to be had if you are handy with a spanner.
Lastly ebay. I have done OK with the bits I have bought but there is a risk...
Enjoy your Mk3. I did enjoy mine a lot.