Is it worth saving my Prius?

I have a 2007 Prius with a little over 150k miles on it. Overall it was working fine outside of my combination meter (it has been gradually getting worse and more frequently going out) and headlights (one, the other or both will go out at random). I was able to cope somewhat with these two issues, up until I ran out of gas because the dash lights were out. When I ran out of gas, the red triangle, as well as check engine lights came on. Since I did not realize I had run out of gas, I had the car towed to the dealership, since it looked like it had died on it's own accord.
I was given a $6,000 repair estimate. They claimed that because I had run out of gas, the computer suddenly recognized that there had been a problem with the mass air flow sensor, supposedly all along. On top of that they also said that the brakes were bad, so I had those replaced, and they were able to "clean out" the Mass air flow sensor instead of replacing it, since I was not ready to pay the money that day to replace it. They said that these were the urgent things, and that the cleaning of the air flow sensor would buy me several months before needing to replace it.
The dash lights have never come on again since leaving the dealership (before they would at least come on a few times a week). Also, the day after leaving the dealership, I got on to the highway and was within about 10 miles of home, when "problem" began flashing on the center screen. This flashed repeatedly, with beeps, and then a few minutes later the icon indicating that the car was overheating came on. My car has never overheated before. I had heard that if you turn the heater on full blast, it could help remove heat from the engine, so I turned on my heater, and it is suddenly not working - it is blowing cold air. I have never had any problems with my heater before either.
I called the dealership to complain that suddenly I am having these two problems (overheating and heater) right after getting my car back, and initially they agreed to "diagnose" the overheating and heater problems (neither of which were on the $6000 repair estimate, because they had never been a problem before). After taking the car back, and leaving it for half the day, they came back and said that in order to diagnose a supposed coolant leak from the inverter, they would have to do some type of procedure to access the area, that would cost me over $700 for the diagnosis! They then told me about how they see lots of "coincidences" of problems developing right after being serviced.
I need a reliable car for work, and I am on the fence on whether to throw money at this Prius, if it will come out the other side and drive for a considerable amount of miles (I've seen that these cars can get up to pretty high mileage) or if It sounds like it would be better to just trade it in for a used Civic.
So my questions are, do these problems seem related? Does it sound like things that can be fixed, and then the car would still have a considerable amount of life left, or the beginning of a snowball of problems? Any ideas on diagnoses? Any other comments or feedback related to the decision would be really appreciated!

Thanks!