first of all welcome to ASC
I hope you enjoy the sport as much as we all do.
For painting, there are a lot of tutorial on youtube on how to paint your gun. all you need is a spray paint. I suggest that you first practice on a piece of wood before trying on your gun.
for upgrades head to either airsoftdepot or torontoairsoft. they will both have the parts you need and you can see how they are.
If you get age verified(highly recommended) you get access to classified on the site. that way you may be able to score some quality parts for cheap ass prices.