If you truly want to get by cheap then just replace the pads, however, flushing the fluid should be a MUST DO. The fluid absorbs moisute over time and when the brakes heat up, the fluid will boil easily and your brakes simply go way. Not fun!
If the rotors are not warped or damaged, there is no need to turn them.
IMHO, on that old of a chassis the entire brake system should be considered for overhaul. On my coach, I had no idea of previous mantenance so I replaced all 4 calipers & pads, the master cylinder and all rubber hoses. The LAST thing you want to have trouble with on something as big and heavy as a motorhome is the brakes.
As far as price, I do all my own work so for me it was just the cost of the parts.
1995 Coachmen Santara 360MB 36' w/slide.
Ford F53/460 chassis, 1990 Jeep Cherokee "toad"