I just got a messed up toyota corrola gt-s 1989 for free

, something is wrong with the engine but from the words of my uncle, nothing hard to fix just need entire weekend 2 do it, . I'm thinking about into putting in some money and effort to fix the car since it had only, 100k on it(still not sure how).
My question is, did anyone have any expirence modifying this type of car, and what's the top pwer and speed he got out of the car. I'm sorry if the threat is to general... but i'm not sure about the car and just wanted some advice.
Any response will be appreciated