[1project2many]

Spent 3 years and a million hours working over panels on my truck. Yep... I know where I coulda done better, too. I used to feel so bad about it I'd point out the mistakes but after seeing plenty of issues with "professional" cars I just let it be what it be. One of the first comments I got on the truck... "Nice, but is there any Bondo in it?" What??!! You don't get a 40+ yr old truck straight without filler. I said "No. I don't use that brand." Then I got to hear a 45 minute lecture about how I shoulda used lead including stories of the legendary "old guy" (he's been dead / missing / lost for years) who could hand build an entire truck out of a single steel panel and never used any filler other than a few old lead fishing sinkers. Sheesh. Mr. Expert couldn't have recognized a flat tire let alone pick out the areas I had used lead.

Spend the time with the firewall. As you get better you'll be able to judge the quality of the repair better and you'll know what's acceptable and what's not so good. But in the beginning you need to work 3x as hard as you think you should to get it right and you'll still find plenty of unexpected "gotchas" along the way. I was lucky enough to get lessons from an old body guy when I was young. "Wax on, wax off" type stuff beginning with wet sanding. I can remember just how many times I had to redo that first car because my eyes and hands just weren't trained to notice issues. Spend the time now and you'll appreciate it later.

And for reference, a "professional" is someone who gets paid to do what an amatuer does for free. Being paid to do a job does not mean the job is done better. Professionals have to earn an income and will generally set a bar for how far they'll go during repairs. You are building a truck to your standards and have the ability to say "I'll have to spend more, but I'm going to do it right."

HTH