Not to burst your bubble or anything, but you did notice the pricetag on that receiver was US$566, and that's not in Canada yet, right?
If you're that keen on going down this route, sell the CA, and get the G&P one, or build your SR25 from scratch using aftermarket parts (the G&P receiver comes with a mechbox, so you're missing a stock, grip, motor and front end). It'll probably be cheaper in the end.
As for painting your own trademarks, you can try... but if you don't really know what you're doing it'll look like shit. (hint: you most likely want to silk screen it)
Your best bet is probably just to cover the whole thing up with a nice camo paint job. Check out some real ones for ideas:
http://www.knightarmco.com/sr_25.html