We don't seem to have a write-up for it, but it'* pretty easy.

1. Move things out of the way. For the front, it'll be just a little wiring. For the rear, the strut tower brace, a couple brackets, and maybe the alternator and its brace will need to come off.
2. Remove the bolts holding on the valve cover, and lift it off. Make sure nothing falls inside while it'* off -- this includes bolts, grommets, dust… anything except fresh oil.
3. Pull the old gasket out of the cover, then push the new one in. It will only go in one direction.
4. Take the rubber grommet off of each bolt, and put on a fresh one.
5. Tighten the valve cover bolts to whatever your year'* manual says (most are 11 ft-lbs, correct me if I'm wrong).
6. Put back anything you (re)moved.

At this point I have enough cash saved up for any emergency that may arrive, but lets hope it doesnt come to that. Now, would some place like AAMCO be able to do this and do it well?

Any garage can do it for you. Save yourself some money and purchase the parts on your own. (I sometimes do that for serpentine belts.)

Should I just ask to have the fluid and filter gently changed?

Yes. As I mentioned, some shops have pressure transmission flush systems, where others have a more gentle fluid change system. You'll want the fluid change, not the flush. I would get a shop to do the flush for a few reasons. Fluid (retail $7 a quart for Dex 6) at 12 quarts is $84, the filter and pan gasket are $15 (they come in a kit), so you're right around $100. However, if you do it, as I mentioned, you can only really drain 8 quarts of it all.

I had it done at Jiffy Lube for $115 out the door.

Zeta'* instructions are exactly what you need to do. Its a pretty straightforward job.

So I was at walmart earlier and I took a look at all of the additives for engines and transmissions... What would you guys say? I've heard that you should just stay away from them.

There are a few, like Seafoam and fuel system cleaners that are great cleaners, which you should use every so often.

Some others, like octane boosters and fuel stabilizers, are useful if you know you need them (for example, if you put regular gas in a supercharged engine).

But for the most part, additives only help you mask the symptoms of a real problem. A real repair is more difficult, but more satisfying at the end of the day.

Going to caveat disagree. On the trans in the OP'* car the two biggest failures are EPC/PCS soleniods and 4th clutch hub shafts. His issue sounds like the EPC and maybe worn valves on the valve body.

Can I get a translation? haha

Ok so a little but of googling has come up with this- my symptoms (Hard shifts when warm + traveled a few miles, goes away when cool) seem to be related to the PCS, as referenced to many other threads I have found that show the same symptoms on a 4T65e. So, does it look like that is the case? Shall I take it to an AAMCO and have them check for this specifically? I'd really like to know, because I would like to fix it, because I plan on keeping this car for at least 4 more years.