Buy a S2 license to get more cars. There are pretty neat looking vehicles also. And yes, some of 'em also has spoilers.
However, this is not arcade game where spoilers are just for looks. They actually changes cars handling, so you must be careful adjusting them.
If you like cars appearance, I suggest you play NFS: Carbon or NFS: Pro street instead of LFS. There you can tune cars appearance without making it uncontrollable.
Car tuning? I will change that a little bit and say something like racing modifications.
maybe 2 or 3 spoilers and bodykits, not for looks like those stupid NFS kits, but to have some differences in aerodynamics.
I remember when i played Street Legal Racing Redline, there different parts added different behaviours on the car. For example one spoiler added very little downforce, other one heavy downforce, and even other one added more stability when cornering.
Changing wheels? I don't think it's necessary, but i won't deny it would bring some fun to the game.
could someone please also tell him the Spoilers, Wheels and Bodykits do not tune your car in anyway tuning is something to do with your cars engine, not your bodywork