You're right, a hobbiest can do stuff when they decide to. The one bad thing about restoring my car is I've gotten so far from the original plan, it's gotten very, very detailed, is now I've actually hired stuff out that I wanted to do, mainly not wanting to screw it up, like the headliner, and yep, I drew the line there. The Seats I was going to do until I ended up in a cast and then the headliner guy offered.
Now I have to decide on installing the windshield myself or not? That's about the last, haven't done before I have to decide on.
I drew the line at the convertible top cover. I started doing it and felt 'over my head'. $750 later I was a happy camper! I don't think I would even attempt it again.
Now a windshield, that's a 'no brainer' for me. If I did my very best I could only come close to what a pro can do. And at $150 installed....well, you know.
One trick I found with the windshield is get an online quote and take that in to the local shop. They will usually match it.