I have a 36Z and your location sounds exactly like mine. I replaced my pump about 3 weeks ago. Like you, I figured I'd have to hire a 8 year old kid to get into the spot where the pump is located

, as I'm 6'1" and carry about 20 pounds more than I should

.
There is no need to remove the water tank. I had a PVC plug that fit the connector coming from the tank, I unscrewed it from the pump and screwed in the plug, I lost very little water. The rest was easy, unscrew the old pump from the base and remove the other hose. Reverse the process on the new pump. The whole job took about 30 minutes and I don't think I lost a pint of water.
You'll have to cut the 12V connector off of the old pump and crimp it on to the new.
It looks harder than it really is, GOOD LUCK