Everything everyone has already said is
EXCELLENT advice.
I would add only a copule of things.
1.) Have a plan before starting.
2.) Set timeline goals for yourself with the already mentioned "mini projects."
If you try to do "too much-too fast" you will more than likely be disappointed with the results. Take your time, yet set goals. Once you reach that goal, treat yourself. A new wrench ... a new part ... something small. This will help you to stay positive in your thinking and makes the job seem more like "fun" and not seem like a "job."
I will bet almost everyone here, at some point in their projects, have felt they are in way over their head. I know I sure have. What seemed like a mistake at first ended up being a learning experience. I have learned to tig weld, color sand/buff, and do some MAJOR fabrication that was way beyond my skills when I started. But the fact that I had ZERO bucks to pay someone else to do it forced me to learn to do it myself. What seemed like a "pain in the ass" turned into something that I wouldn't have learned otherwise. When you run up on these sort of obstacles, tTake a break for a day, or even a week, or two. You will be amazed how anxious you will be to get back to work once you are away from it for a little while.
BTW: I am in year 4 of a frame off ... that started as a two-weekend rocker and cab-corner replacement.
Most important is to HAVE FUN! If it isn't fun, then it's a job.