8G 2.4L auto trans questions

Hello all -

New to the forum, and did a bit of lurking before joining. I have some specific questions pertaining to my attempts to repair my daughter's 2000 Galant (in signature).

Tranny has started recently to make a fairly audible whine/howl noise when in gear (does not do it in park/neutral). I have realized that it's probably time for a tranny rebuild or swap; the vehicle has 225k miles on it. I am third owner, but knew the 2nd owner for many years and trust that it's not been abused. But nothing lasts forever. I'm not a novice to cars; it sounds like a bearing starting to go bad.

Over the last few years, this car has be updated nicely with solid work. The buddy that I bought if from had me help him maintain it (he was not mechanically inclined, but had the $$$ to pay for all the stuff, so I did the work for beer and pizza!). So, it's in such good mechanical shape I hate to toss it aside. I am very good at mechanical work; not afraid to tackle big jobs. I've personally replaced the entire engine timing set, the cam lifters, the MAF, the harmonic dampener, the struts and shocks, the CV axle shafts, ball joints, sway links, etc, etc. The car drives fantastic, as if new. So I would like to either repair this tranny, or swap in a lightly used one, and hope to get this to last another five years so my daughter can have it through college.

What I'm looking for is info that will help me ascertain the parts/components I need to do the work. Regardless if I repair this myself, or buy a used trans and swap it in, I need to know the tranny make and series (something like a typical alpha-numeric character string ...) so that when I order parts online, I'm searching the right criteria. As much as I've searched many sites over the last several hours, I've not been able to find any clear delineation of the info I need.

What things should I be aware of to make sure I get the right replacement parts or replacement trans? If I thought I could repair the tranny for a low cost, I'd attempt it, but I have no experience with auto trans units. Engines are second nature to me, but not trans. But I'm not afraid to try something if I have good info as reference material.

Here's where I need help ...
I have no idea which trans series our car has, or much about them. I know the engine 4G64 fairly well, but know nothing of the trans. It does have the external filter on the top, and that's about the extent of the knowledge I have.
- is there more than one series of auto trans for this 2000 2.4L? (I know about the external filter on some, but are there other traits that would distinguish between series?)
- is there any identification markings/tags on the tranny that would assist me in identifying the trans? Where located if so?
- is there anything so unique about this trans that I would be best just walking away from it?
- is there a way to decode the VIN to find out the tranny info?
- is it even important to have the external filter, versus the flat-top trans, or are they basically interchangeable?

I want this to be as much "plug and play" as possible and not have to drill holes, grind clearances, splice wires, etc. I am not wanting to force something to fit; I want direct replacements which will give reliable service for the upcoming years.

Is there a more specific website or link that would help me find this info?

I have found several used trans on ebay and other sites; about $400-700 depending upon age/distance.

I need to get another 100k miles max (perhaps as low as 75k miles) out of her over the next five years and then she can die a quiet death. I do NOT have the money for a new car, as college is going to suck most every penny we can scrape up.

Any info regarding trans identification, markings, traits, suggestions, fixes, etc would be greatly appreciated.