Hi, I recently bought an automatic 2001 Volvo V70XC. It has 150k miles on it. The previous owner said the owner before him rebuilt the transmission at 100k miles, and the issues with it started showing up as I drove it more. I'm pretty inexperienced with working on cars, but I want to learn more and bought this car to work on.

The first issue is when I shift between drive, reverse, and neutral. The shift gets delayed up to 2 or 3 seconds. 

The next issue is that sometimes when shifting the car revs up for a second before the next gear engages. I can't quite pin down what gear it does it in, and it happens less than like 5% of the time. I'd compare it to pushing the clutch in a manual car without lifting off the gas. 

The last issue happened only twice in the 2k miles I've driven it. At highway speeds the car would shift, and the whole car would shutter. A check engine light started flashing, but then went away on both occasions. I took it to an auto parts store to see what the code was for the check engine light, and they said it was a misfire on cylinder 3.

I made the mistake of taking it to the dealership because this issue seemed over my head. The transmission service cost me 1k, and they told me part of that was that the fluid was expensive. The only other thing they did than changing the fluid was retuning the automatic transmission. They also talked me into changing the spark plugs and inspecting the ac system and their regular inspection that came with an oil change, by the end of it I was out 2k. Almost what I spent on the car. They quoted me another $1.1k for replacing the A/C compressor but I couldn't stomach that. I honestly don't know if I was ripped off or not, I try to give people the benefit of the doubt. 

None of the issues have changed. The delayed shift is still there, the revving up still happens, I haven't driven it enough to see if the third issue still happens. The car just doesn't feel confident when I accelerate, like it would break if I put my foot down. 

I think I know what the problem might be, let me know if I'm wrong. I heard that the earlier V70XCs transmission was an unreliable design from GM. The revving issue and delay issue I think is related to the torque converter being bad. The only other theory I have is that they didn't actually change the fluid at the dealership. I'm still trying to figure out how to check.

My main questions:
What do you think the issue with the transmission could be?
Should I try to repair what I have, or do I need to start saving to bite the bullet for a new transmission?
If I get a new transmission, should I try to get a more reliable one that fits it?

Apologies for the long post.