the first thing you need to do as you have admitted you are out of your depth with this is take it to a reputable tuner and get it fully checked over and setup in its current form as you dont want to risk something not being right and blowing it up. if your upto doing a service (plugs, leads, oil, cam belt if its needed or not known when last done)and can check the brakes are in good working order then do that and then get it on a trailer and to a decent tuner. loads of people on here with rs turbos will be able to advise you where to go and i wouldnt let distance put you off going to the right tuner rather than picking a local tuner just because he's local!

once its all running right, has mot and you'r able to drive it on the road then and only then should you look at upgrades. no point upgrading an engine that doesnt fucking run right in the first place!