Water stains and mildew

[Ted]

A couple of months ago I took my Yuma in to have the heating element in the air conditioner replaced.  It sat in my driveway for a while, and when I opened it up on a recent camping trip, I discovered that the mattress that goes underneath the A/C unit was wet (we've had rain) and there are water stains on the underside of the sunbrella material, and also mildew on the subrella material on that side of the Yuma.  Anyone have suggestions for removing both the water stain and the mildew spots?
 
I plan to take it back to service company to have it resealed.  I suspect whoever did the repairt did something to break the seal.