This is very hard to anyone to give advice on. Who knows what kind of work your neighbor is going to do. My experiance has not been good with this sort of arrangement. I have personally seen it only a few times, but when you have a guy "prep" the car and then take it to one of the "McPaint" shops like MAACO, you are throwing away money. You might as well just take it to MAACO yourself. The guy will tell you he gets a "deal" at MAACO and that he will pass that on to you, BS. He tells you that "they spray all day long and they are good at that, it is the prep where they cut corners", again, BS. There is some truth in it, but it just isn't so cut and dry.
MAACO's paint, prep, products, ALL of it is "OK" for a driver in most cases. I have seen some REAL bad work out of them too. And don't, PLEASE, don't let the super nice restored car that is owned by one of the employees sitting out front influence you. God I hate that restored super nice car scam. Your car will NEVER, EVER, look anywhere near that kind of job. Yet they always seem to have one out front "yeah that is one of our painters car that will be painting yours" BS.
Take your truck right to MAACO if you want a cheap paint job and see what they want to do it.
"Seal the whole thing" means that the truck will be sealed with a sealer just prior to painting right in the booth. The sealer is like a primer but needs no sanding. So you apply it, to get a uniform color and substrate, and then just paint right over it in a half hour or so.
You can "Prep" it yourself, sure. But it isn't like we can give you a few tips and you are on your way. Your compressor may be too small and you will be limited to doing small areas at a time.
The first thing you would need to do is have some primer over the bare metal areas. To prime the whole thing is NOT needed if your paint is solid and only faded.
I have to assume any welding you did with trim holes and the like will need some filler work to smooth it out, have you done that?
Brian