Definitely just try to clean it up. Get it mechanically sound (Check your mileage, O2 sensors etc) whatever is holding it back (Low power). I'd focus on fuel metering and delivery. Love the idea of painting the rims black and polishing the beauty rings, cool idea.
See if you can find someone that can sandblast locally and remove the rims and have them done well. Have them powder coated and painted. Will really look different than just painting them.
Without lowering it I'd keep it stock as hell until you're ready for that. Lower it right if you're going to lower it and time it with replacement rims. As you dig around you'll find really good deals (just dig and dig) until you find em and have the lowering job done (Or do) and slap em on. That's the number one thing you'll love about the truck's look is when you lower it.
That radio location looks like it could handle a double din unit so yea there's that =)
You could learn how to take off the door panels, sound deaden the doors before you do ANYTHING so you get the most out of the components. Select components with a decent crossover. Do a couple side firing 10's or 8's in the right box and you'll love the system the entire time you have it.
As you're waiting for it, do the research for the big 3 upgrade, collect the wire, deadening and do the system right piece by piece.
Start a build log and we'll all follow it =)