not a lot. any mods that you do like air filter, cams, exhaust also have to be declared to your insurer. but, they may not raise it as mch as an engine swap.

to be honest mate, your best bet is to keep it standard. just make sure that it is in good tune so you're getting the most mileage out of your petrol, and as much power potential as it's got.

i wish at your age that i had done that, and was able to drive around sensibly and economically. that way you'll save money on petrol, speeding tickets, maintenance, breakages, crashes, insurance etc. save it all up and you'll be able to afford a better car sooner than your mates who go thrashing it around everywhere.

sounds boring, and you're only young once, but it's better in the long run.