Sketchup does let you save and import models. There is even a model warehouse online for people to share their own models (select File -> 3D Warehouse -> Get Models...).
There is a decent amount of pre-built arcade related stuff, but I have a feeling that will grow as more users adopt it for their own projects. If you do a search for arcade, for example, you will see some models of cabinets, components, etc. Searching for mame gives some good results also, including some models made by XyloSesame (joystick, pushbutton, coin door, spinner, trackball).
Also, check out the project announcements here on BYOAC. Artifact has shared his plans, as have other users also. It's a great (free) software package, and with a little practice you can learn to model things surprisingly quick. Good luck.