So I agree with Mac here - the *ideal* way to do this is to buy a cheap engine that's "OK" and pull it apart and do a budget (but thorough) rebuild on it and when its done swap it over. Its not anywhere near as hard as you think but its also not a trivial undertaking. If you do it properly, you will need to have the block and head checked and machined if needed (assume yes) and if you are like me and you decide to put in a new performance cam and other goodies you wind up spending $2K + the machine shop cost ($1K?) but you get a brand spanking new engine. You then borrow or buy a cheap Harbor Freight hoist and do the engine swap in a day in your driveway with a mate and Youtube on standby. You will have the added benefit of a deep understanding of how the engine now works and a ton of confidence, but you will need more than a basic set of spanners.
OR
You accept that all you actually want to do is fix the noise and give your 4 litre a life extension of another 50,000 miles so you do an in-frame replacement of the pistons and bearings only. Maybe you throw a new head gasket at and a sump gasket / RMS while you are in there. Don't touch anything else and reuse all the other bits. Dont open the crank bearings, don't mess with the timing system (chain is loose? SO WHAT! Leave it....) Order the piston's, rings and rod bearings only after you have removed them from the block. Get someone else to put the new pistons onto your wrist pins if you don't have a small shop press handy. I installed new pistons using a bit of scrap steel material, made up a small jig with some bolts to set the wrist pin depth, heating the rod ends with a butane torch and popped the frozen wrist pins in and they worked a treat.
What's the worst that can happen? You've sunk $300 into the engine and its fixed it or else there is a more substantial issue in which case you can reuse those pistons in the full rebuild anyway. The temptation to fix everything and completely refresh the whole motor will be strong, but understand that 90% of what you replace/upgrade is going to make very little if any difference in the medium term. Most new parts you buy will be crap and nowhere near as good as OEM anyway! The big exception to that is pistons: new pistons/rings/bearings are well worth doing as the factory pistons are known to be break prone.