If you pull it of may be a good time to get it ported aswell!

Powdercoating all depends on the shop/cost of meterial ect, you may want to call around and see what different shops charge/ see what kind of warrantee they offer with it, they will probably want one that is stripped to just a shell

Painting it you deffiniatly want to use a paint designed for engine/high temps,

I would almost suggest picking a differnt one off craigslist or a demod sale ect, and have it done to that one so your car is not down in the mean time

Wouldn't be a bad time to do the lim gaskets aswell