Surely it should be UVmapped, because this way it will possible to have multiple textures: Power, Varia and Gravity Suit are basically the same thing, with different color schemas.

Creating the helmet as a separate prop is a great idea! In many amazing fanart images, Samus is depicted without the helmet, and be able to recreate them would be wonderful.

I can be of little help regarding the technical aspect of the modeling work  (otherwise I'd be able to model it myself!) but I can provide a gazillion of reference images and measurements.

For example, this is a concept art of the body inside the suit (flagged for nudity to be safe). It's not anatomically perfect, but it's a start point (besides being a very good art).

Giorgio

giorgio_2004 here, ksabers on XBox Live, PSN  and everywhere else.