We'll assume you have no issues with fluid level, etc., since you recently changed out the fluid & filter (for the 2nd time, so you know how to do it, and what fluid to use). If so...
I believe what
@TJBaker57 is talking about is the TCC (Torque Converter Clutch) valve. The trans is set up to continually slip the converter for both improved NVH as well as a tiny improvement in FE. The problem is, there's so much back & forth movement of that valve in the valve body to produce that 'controlled slip', that it eventually wears the bore oversized.
When that happens, the trans can't maintain steady state fluid pressure, and
eventually, a TCC code shows up via a CEL on the dash, and a OBD diagnostic code. At that point, it's time for a new valve body (which is made out of aluminum), or an oversize TCC valve to be installed in the existing VB (via reaming the bore and installing a steel sleeve.)
Depending on how mechanically inclined you are, a new VB is installable without removing the trans from the vehicle. If the trans operates normally, otherwise, this can save a bunch of $$$$. However, at 200K, most 4L60s are near / at the end of their design life, so you could do all of the work to put a new VB in (or have the existing one repaired via the boring out / sleeving / oversize valve), and the trans might fail soon after.
Your reaction to that will depend on whether you were glad to get a few more miles out of it (and likely ready to move on to another vehicle, anyway), or whether you thought you'd get another 100K out of the unit (and, thus, disappointed, and spending more cash, too).
If the issue is caught early enough, there's a kit by a company called TransGo; it converts the TCC continual slippage to a straight 'on' / 'off' function (like a traditional converter lockup; kinda feels like a 5th gear engaging). A lot of people on this site have put that kit in, with good success. But, again, it pretty much has to be *before* you encounter problems.
If you decide to put in a new VB, putting in the TransGo kit at the same time, along with some other goodies, will keep the TCC valve from wearing the bore oversize in the future, as well as preventing some other potential issues. But -- as I mentioned above, there is some risk, given the mileage of the trans. It could last forever, or it could go out right after you put the kit in (but
not 'because' of the kit, if installed correctly).
As far as replacing the entire trans... you could go with a junkyard / craigslist replacement (cheapest option, $500-$800, but no knowing how it ran before the vehicle was scrapped), a rebuild of your own by a local shop ($1800 and up, depending on what they do / replace), or a remanufactured trans by a company who will ship the thing to you, and you either have it installed by a shop they approve of (for warranty), or you swap out old / new (and return the old one to them, as there'll be a core charge involved). Again, this option will likely be similar in cost to the local rebuild, depending on what you choose (certain weak areas of the 4L60e can be addressed during a rebuild, for a little extra $, over a 'OEM-style' rebuild).
There are still a couple of areas that will remain a bit weak, because they're engineering issues that can't be resolved through design, alteration, or hardened parts. This is true of all 4L60E transmissions. That's not to say they suck - they don't, and they're considered a solid trans (especially compared to some competitors.) GM has a good rep with rear-wheel-drive (longitudinal) units, going all the way back to the 'Turbo HydraMatic' 350 and 400 (the 4L60E is a direct descendant of the 700R4, which itself is based off the THM350).
So... you know you will need to repair or replace the trans (or trade the TB for another vehicle), and you need to consider the condition of the rest of the vehicle, and how partial you are to it. As far as the engine... if you've kept the oil changed, it could *easily* last another 100K. You have the V8, and that's a member of GM's LS family. I do see you have a '05-up engine, so that has Displacement On Demand (DOD), which can cause issues. If you've already had the DOD removed or tuned out, the rest of the motor will live a long, happy life (you might have to replace a seal or gasket or water pump somewhere, but the motor will run without issue, outside of the DOD).
If you decided to rebuild / repair, and keep the vehicle, put in an external transmission cooler. Doesn't have to be a huge one, but it'll protect your investment.
Also, don't wait until 300K to do the next change of the fluid / filter. 50K is a good service interval. Some people here do 30K.
