Above all else, enjoy! It sounds like you've got that part doen! Tuning and all that will come with more and more experiences. All part of the fun!
As far as the paint goes... A LOT of it IS the prep work!
I should throw in here, yes, there are things that you will want to upgrade and change for the kind of driving or racing you do. There is a point however where you are changing and upgrading for the sake of changing where it's just not necessary. If you start snapping a-arms, upgrade to rpm for...