Can the Surface Pro 3 utilize its full memory?

I've been shopping for a Surface Pro 3 that I'd like to upgrade to Windows 10. It occurred to me, I can't find any info on if devices like this have x86 x64, etc. or what ones they use. If I put out the money for a Surface Pro 3 with 8 GB and upgrade to 10, is it going to be able to use more than 4 GB? Or will I have to get an entirely new OS on top of it? Can you reformat these things through USB or will that void any warranties?