+ HRDennis pointed out, in similar thread, that Home Depot rents "jumping jacks" (or 'whaley packers', as they were called when I was a journeyman plumber). Both Home Depot and Lowes sell hand tamps.

+ A sump pump is probably the best way to drain the pool, and will be useful to you, as long as you have that pool. I was going to give you an Amazon link for an example and then suggest you go to General Tools, but the Amazon pump is as cheap, and much better rated:
Superior Pump 91250 1/4 HP Thermoplastic Submersible Utility Pump
+ Building a low retaining wall has become MUCH easier, since they introduced these interlocking block, a number of years ago:
http://www.lowes.com/Outdoors/Pavers.../N-1z0wga9/pl#!

Lowes even has instructions:
http://www.lowes.com/projects/garden...g-wall/project