I could be wrong, but I believe lighting for Unity is defaulted to dynamic, realtime lighting. I've been told there is a setting to change that allows light maps.
views -> viewport configuration -> adaptive degredation Some of the options should be on by default, editing can still be slow with it on but it will make moving around the viewport rendering faster.
By default the noise procedurals are waaaay strong for height but when you lower the opacity in the height channel to (in the case of this grip material) 3 or 4% its fine ;)
A very good model but as said above I would try to mess with the lighting, the default skies are very good and are a great place to start in toolbag 2!