I'm in about the same situation as you... can fabricate and weld but beyond that I'm pretty much out of my comfort zone.
Painting is the (relatively) easy part. It's the work that goes on underneath the paint that will break your back and try your patience. Not sure how much else you're planning other than paint but start rough and work progressively finer with your body prep.
My first step was to strip off all the paint then run a DA sander over everything to get a rough surface so the primer gets a god bite.
Apply one coat of primer. This will act as a guide coat in your hunt for high and low spots. Block sand down to metal to reveal high and low spots. I used Rage Gold filler in the low spots and sanded with 36 grit on an 18" block by hand.
Once that's done lay on a couple good coats of high-fill primer and block with 80 grit dry to fill the sanding scratches. Fill any low spots with two-part glazing putty and blend. Lay on two more coats of high fill and block with 80 grit dry. Repeat this process until you can block out the entire part without hitting metal or finding low spots. Note that as soon as you hit metal stop sanding that spot. Continued sanding will keep cutting the primer but not the metal.
At this point get a rag real wet with with prep cleaner and mop it over the surface. This will give you a real good idea of how smooth your panels are by the reflections.
Now lay on two more coats of high-fill and block with 180 dry.
As a note: Do not just sand in one direction, do what is known as x-sanding, a self-descriptive term describing the direction you sand, in an X pattern. The object is simple, when you sand in one direction you create ridges in that direction, sanding no quite perpendicular to those ridges smoothes them out. DO NOT chase low spots after hitting metal! Fill them in. When you are done you should be able to block sand the guide coat off the entire panel without hitting metal or finding low spots.
When you're done with that block with 400 grit wet and then paint. Add a little detergent to the water... just works better that way.
Be sure to use a good guide coat. I know a lot of guys just mist on a ghost coat of flat black but after trying both, I much prefer work with
3M Dry Guide Coat. I'm still blocking so no meaningful advice on the final color coat... yet.
One more thing... PLEASE wear a respirator when you paint, indoors or out.