It's pretty easy to check...pull the backplate off and look for rust...turn it over and listen/feel for roughness in the bearings.

If you need to change them, there are numerous tips in the Glow Engines forum...and there's a good a tutorial on changing bearings on youtube.

It's pretty straight-forward, changing bearings, and if you've got mech. experience like you've mentioned, it's a piece of cake to change 'em.