I did that job once--many years ago. I think you'll have to at least remove the window glass to get the rear channel out. The gold colored clip is what hods the regulator "pins" to the lower channel -- and the third leg of the regulator to the door frame (I'm thinking 240 here--but I think your third photo down shows that part just below the right side of the plastic housing). You have to work backward with your hand between the lower channel and the outer door skin. The folded over end of the clip has a raised edge to push with your fingers--lift it a little and push - then wiggle the clip off the slots. You can practice on the one you can see facing you in the inner door skin. The clip and washer you found are probably left over from a previous break-in as you surmise. -- Dave