Welcome mate, hope the Z hunting goes well.
1. Common Problems and anything to check?
Main problem is a clicking rear axle, which you should be able to hear when you set off on a test drive. Still relatively cheap to repair eg £300 ish. Some Bose systems skip when playing CD's so might be worth bringing one with you. Always HPI check the car and then it's just the usual things when buying a car. There's not usually any major things that will cost mega bucks.
2. General things to look for?
Only what you would normally check when buying cars, main problems IIRC are answered in 1. No probs getting an import, could save you £££ but for some reason they cost some people more on insurance so check that out first
3. Anything to stay away from?
Personally I'd avoid any car that has already been turbo'd, supercharged or nitroed as engine can be fragile if it's not done correctly. Would only consider one if it was a user on here tbh. Apart from that avoid Orange/rusty cars as it's well known that they have much less power - don't they Tim
4. Any recalls on things?
There has been a post for recalls recently for 07 cars, should be able to find it if you do a search. Don't know of any others.
There's plenty more info on here if you can find it. I used this site to help me nefore I bought my car. If you are thinking of a specific car and want advice just post up. We are an opinionated lot tho. . .