That's a really fine machine you've chosen
Top of the line. I see that the kit is quite a bit less costly, a good choice for experienced DIY's. The tricky part of the assembly is to get the hydraulic connections thigh. Not tighten too much, and risk ruin threads and gaskets, and not to little. If one never have been involved with this kind of machinery, before, my best advice is find some one in your local area with experience in the field, to give advice and help.
About painting, get a professional in the field to do it...I would use 2 component epoxy paint, same as use for cars and machinery. Powder coated is even better, but maybe a bit 'overkill' with this kind of models, which most of the time sits on display...But if one find the cost for powder coat no problem, so go for it. (Powder coating is a process that's involves heat treatment, and one need considering removing all plastics)