Newbie with rooftop A/C blowing hot - self repair?

[littlepeartree]

Hi guys, I'm a newbie, just bought a 1995 Thomas Vista 6-window shortie with 140k the other week and starting on my conversion.

I'm taking it to a bus repair shop tomorrow to get a second inspection and to diagnose the gas gauge which is not reading properly (I think there's an issue with the floater, ran out of gas in the middle of the Arizona desert while showing half a tank when I was driving the bus back home from the seller - that's a fun story for another post). The rear A/C unit is also blowing hot and I'm trying to decide if I should get them to repair that as well or if I should attempt to fix it myself to save some $$.

I purchased the bus through Public Surplus direct from the school district, the listing stated that the front a/c was inop and the rear A/C was working and blowing cold. I was informed upon arriving in Arizona that it was now blowing hot - I know that all auctions are considered As-Is buyer responsibility but do I have a legitimate complaint that the auction listed the rear A/C as operating and cold when it in fact wasn't? I tried to see if it was something they could handle while I was at the bus depot with the seller but didn't get anywhere... not great at being pushy. Ended up being a hell of a trip back through the Arizona desert in August with no A/C, almost gave myself heat stroke...

The seller who walked me through the bus believed it just needed to be charged and recalibrated, given that the bus repair places near me charge $150 an hour for work, is this a task worth fixing on my own? Time is a component as I have an inaugural trip planned in two weeks so I'm figuring I'll probably have to pay for the privilege of expediting the process, and I have to bring the bus to the shop anyway so might as well do it all at once?

Advice appreciated! Attached the pic from the auction, will update later with up close pictures of the unit and info when I go work on the bus later today, it's currently being stored an hour away. Very much new to all things bus related beyond my skoolie.net education..