Brake and Belt issues on my '88 345

[Mr. D]

With cold weather starting in Michigan I decided to let the local RV place take a shot at my rear brakes, started to hear them grinding. Anyways, a $350 job turned into an $1193.00 job, seemed high but I seldom get a "brake" on prices. As usual, one job opens up another, I now have new rear rotors, caliphers, pads etc. but in addition I need new front pads. I have done many brake jobs, both drum and disc, on cars and trucks. Besides being heavier are the front disc brakes on my 345 basically the same job or are there other concerns I should be aware of? In addition, the mechanic said that I needed a new brake controller for my rear tag axle brakes(elec. drum). Does anyone have info on that job? And lastly, two summers ago I took out the engine AC radiator and used the space for new and much larger engine oil and transmission coolers. While exposed during the job, I replaced all belts, hoses, water pump, fuel pump, what ever I could get my hands on. The only problem has been with the lone V belt that operates the old AC compressor(no longer in use) and the power steering and brake booster. It constantly needs adjustment to stop squeelling and will eventually wear out, I have replaced it once already. I have a serpentine belt on the rest of the engine. Anyone ever have problems with this belt? It appears that the only adjustment is a screw on the side of the compresser. When this belt breaks I have no brakes or steering so you can see my worry. Any advice would be welcomed, Mr D.