My personal choice would be to skip that PC. I'd rather have my trusty "can play anything even if it can't necessarily max out the graphics or frame rate" PC than a "Skybox" PC. Hell, as per the OP it's not even allowed to use gameplay-altering mods, just graphics mods.
Skyrim was a great game for me, even with the "vanilla" mechanics, but if it's the only game the PC will run then gameplay mods would have to be included or it's a bust.
"Before I send them to hell, I shall let them see heaven." - Claptonvaughn, http://www.gamefaqs.com/boards/605432-path-of-exile/68145584#11