How should I complain? What do I really want?

I took my 1978 Mercedes to a local shop to have the windshield and rear window gaskets replaced. It took him almost a month to do and he did a very poor job of it. He completely failed to install the metal trim on the windshield and it must be removed for me to install it. He also used window sealer around the gaskets on the paint. If I take it back for him to do again, I fear he will do a worse job and mess things up worse. Almost afraid to complain. I think I can fix things to look right, but they wont BE right. Even if I take it back, what do I want? I can’t do without a car for another month, and parts cost would be prohibitive. Aaugh!