Timing belt is imperative. If it breaks you'll need anything from a few intake valves to a whole new engine. While you're replacing the timing belt, also change the tensioner and the passenger side engine mount. The mounts especially are weak spots on these cars - you'll probably want to change at least the front and rears too - they're pretty easy. (Passenger side will need pressed into the bracket.)
Step one btw: Get yourself a Bentley manual. There are other manuals out there, but nothing even comes close to the Bentley - it's very complete. eBay / Amazon etc are likely good places to go shopping.
Parts. I would suggest www.germanautoparts.com and www.parts4vws.com. Mechanical parts aren't too bad to come by for the most part, (a few 16v specific bits are scarce) but the Scirocco-specific bits (trim, body panels etc) are pretty much a "find it in the classifieds" thing. The Scirocco is built on the A1 chassis, so most mechanicals will interchange with the Rabbit / Cabriolet / 1st generation GTI.
Mark your calender for the 1st weekend of June, and rule #1 in the Scirocco forum is of course post some pics of the new ride!