I have a similar fear of bike shops. The one thing I don't do, as others have said, is build wheels. I know one really good wheel builder who built my commuter rim on my rear hub. I recently took a set of wheels for a tension and true to him specifically. He was a little backed up and I didn't mind waiting. I happened to call to ask him a quick question (rim ID) and the guy who answered the phone said today was his day off, but my wheels were being worked on right then.
Now I don't know if he said that because I was calling to have the job rushed and they weren't actually on the stand or what, but I said "No, no, that's fine. Please let XXXXX do it tomorrow. No rush, please." Anyhow, he did them the next day and I was super happy because he said he's been busy with lots of smaller repairs and he didn't want to rush the job because he wanted it done right.
And speaking of bad mechanics, some shops are charging major premiums for basic, basic services. I visited one shop in Dallas where a guy brought in an old Schwinn with
friction shift and they told the guy a tune up would be 55 dollars BEFORE parts, such as cables, etc. That's pretty rough in my opinion. Don't think I'll be going back there anytime soon.