Well I'm going to guess that you have quite a few miles on that, at least in the 160-180k range?
P0742 is the torque converter clutch stuck on code. That's usually the fault of a $17 solenoid (TCC solenoid), and is accessible from the side cover. Which of course requires dropping one side of the subframe, not hard but requires a good amount of tools and time. That will probably have to get fixed, it's not going to get better.
P1811 is usually the fault of another solenoid, the PCS. This can be covered up with a shift kit, but seeing as the TCC solenoid needs replacing, you'll probably just do them both, if at all.
And loosing overdrive is the result of the 4th clutch hub failing. That takes a little more work to get into the trans, but as an average DIY'er like myself, I just replaced those 3 things in my trans not too long ago on my own.
Also those temps are not abnormal, have you checked the coolant level? What was the ambient temp outside at the time?
So at this point a shift kit and fluid filter with lucas trans stop slip may help only with P1811, but seeing as the fluid is dark that makes it iffy. How dark are we talking? And do NOT flush it, that's probably a 90% chance of killing it, especially at this point.
Do you have tools to do things like dropping a subframe a foot? It takes 2 jacks and jack stands, 33 or 36 mm socket, socket set from 13-19mm, torx bits up to T40 etc. Overall it depends on if it's worth it to you to put the time and money into it, and of course the risks of it failing from something else soon.
