Here is an old article about converting a similar size trainer to electric. It is a bit dated using NIMH batteries and an inrunner motor but you can still glean some good info from it. Probably the most troublesome thing will be locating the battery pack. Unless you create a battery hatch you may have to remove the wing every time you want to make a battery change.
HeadsUpRC carries most of the stuff that you might need. They offer $2 flat rate shipping and ship quickly. Check with the folks at Heads Up (HURC) for recommendations regarding motor, esc and batteries.