id say do it, IMO if your gonna build up a car, do it with something like this thats original, and will turn out to be really fun in the end, and actually become a better car than it started out being. not with an already well made and balanced sports car that your just gonna screw up.
I wouldnt do much for the engine, i dont know how quick these are stock, but id put all my money into a legit suspension setup, coilovers, front and rear sway bar's, poly bushings, and a lot of chassis reinforcements in the right places, because im assuming a car like this has a fairly flexable chassis, which will only become more noticeable as the car handles better. get some nice light wheels with a good offset, dont waste your time with getting 19's or anything, stick with 16's or 17's so you can still use it. plus 16's or 17's with a nice stiff sidewall tire will handle better than some super low profile 19's.
as for the engine, stick with the basic's exhaust, intake, ecu reflash, etc.. stuff thats gonna keep the car reliable. unless the car's just unbearably slow, but even then you would be surprised how fun it is to have an extremely slow car that handles like crazy. for a street car, id almost say its more fun than having a shit ton of power.