Pretty much exactly what was stated above ^^^
I myself grew up in a shop, and have always been around cars, car parts, accessories, etc, etc, there are a few things I still will not tackle myself but for the most part (unless it is extensive body work, or custom tuner a car that is not supported by Diablo Sport and their CRM software (which the FT86 family is not)) I can get it done with no problems.
Personally if I were you I would read the forums, read the DIY sections, follow the instructions that comes with whatever parts you buy when you install them.
If you have an issue when installing or understanding the instructions that comes with the parts then ask the forum members.
Also make sure you have the right tools for the job that is most important IMO having the right tools makes your life a lot easier when modding the cars.
When you want to get into more extensive mods if you are uncomfortable doing them see if you can find a shop that will let you watch them do it, if you have friends that know about cars see if they will show you a few things.
It's all about baby steps just like with anything else when you are first learning 1 step at a time, and you have to crawl before you can walk, and walk before you can run
