Sorry to hear you are having issues with covering the cost for repair.

Did you get a list of parts that from the quote that needs to be replaced? Back in the day, automatic transmissions had very complicated valve bodies and required full removal and cleaning. Now they are all controlled by solenoids which make them easier to repair. These solenoids can be replaced rather simply or the entire valve body can be replaced as a cartridge. This all depends if there is room to access the valve body. I'm not sure if it can be done while the transmission is in your vehicle. Your transmission should be a AW55-50 which is shared by the Volvo.

If it can be done while in the vehicle, then the cheapest option is to replace the solenoids. You can find them on eBay. You need to make sure they don't get mixed up. Each solenoid has a specific location.

Here is a link that has instructions to remove the valve body:

https://www.repairprocedures.com/service-manual/document/2006/chevrolet/equinox/transmission-transaxle/control-valve-body-replacement/2789_1313_8236_37886_8_1382471.html

Here is a video of the solenoid replacement. These three are usually the culprit and the others don't need to be replaced.

I found the entire solenoid set on ebay for just over $100. You can find less expensive kits with just the 3 solenoids, but I don't know which is causing the problem. I also found the entire valve body on ebay for $267.

Make sure to replace your transmission filter while you are in there.

Your transmission is an adaptive transmission and will require you to perform a procedure of shifting gears to learn shift points. There are procedures on line on how to do that or the procedure may come with the valve kit.