yeah, i think the first thing you need to do is decide how much you want to spend, and if you CAN keep the truck if you get teh motor fixed cheaply enough. but before all else, do this.
go through and double check each spark plug is tight, and that each plug is firing. check if the gaps are all correct on the plugs. try cleaning the injectors as well, sometimes a dirty or bad injector can cause alot of problems following the symptoms that you are describing, as was the case on a friend of mine’s mom’s taurus, above a certain RPM it would knock funny and really lose power. if all these check out fine, i suggest pulling the valve cover again, and post some pics for the experts on here to peek at and give some input. if you really want to learn and wouldnt mind the work to save the money, i for one would be more than willing to lend a hand, and there are plenty of people on here that you could borrow all the tools you will need for the swap if need be. call up HOW-BILL here off bullis road, they specialize in small trucks and 4x4,s and im sure they will have a motor for you for a decent price. so looks like all that is left there is to find a place to do the work. hell, with the people on here you could probably sit back and watch as we do everything for you provided enough food and beer is present. anyway, thats just my thoughts on the situation, its something you whould seriously weigh out on paper and see what would work out best for you. heck, even doing the swap yourself and still selling the truck would save alot of time and money.