You should go right now to the auto parts store and pick yourself up a voltmeter and a vacuum pump. You will be in heaven with these two tools.

You really can't diagnose any electrical components without a voltmeter unless you want to start switching parts out from one side to the other. I think the window motor is the only thing you could really do that with anyway.

It will save you tons of money in the long run because you won't be replacing perfectly good parts because they 'might' be bad.