My hardwood floors are sealed with urethane/polyurethane and someone tried to wax them. Now there is residue/hard wax buildup on the floors removing the shine and making them look terrible. What are my options for removing the wax and restoring the integrity of the floors?

Who's bright (but bad) idea was putiing on the wax? Anyway, doesn't matter. You will have to get some Varsol, and lots of rags and wash the floor down as many times as it takes to remove ALL the wax. Maybe the guy who put it on there in the first place can do this?
This shouldn't harm the urethane underneath, but there must have been a reason for the wax application in the first place. If the original finish is is good repair, you can the buff and coat the floor with a fresh coat of urethane; if desired once all traces of wax have been removed. One potential problem is if during the disolving and removal of the wax drives it down between the boards, when applying the fresh coat, you MAY end up with cloudy lines along the edges of the boards. (called wax burn)