Are you planning on doing the timing belt yourself? If so, nice one! Thats the one job I never want to get involved in, mainly because I know I might forget something, start the engine and BOOM!!! one fooked engine . I would get it done mate, just for your peace of mind really and for the sake of a couple of hundred quid. Have you inspected your timing belt? There are usually tell tale signs that it hasn't been replaced for a while, such as discolouring, cracking, worn teeth. If you've got the parts, then take it to your local independent garage to fit for a bit cheaper and would save you the hassle.
BTW I love your sig , I've only got the first 4 done