Shouldn't be too hard to reduce it by hand if you know your way around edit mesh and edit poly. I wouldn't trust an automatic reduction algo they tend to make a mess.
I guess you know enough to check the modifier stack and make sure they didn't just meshsmooth a whole bunch of times to add a bunch of itterations from a mid to super high poly mesh for normal maps?
I guess you know enough to check the modifier stack and make sure they didn't just meshsmooth a whole bunch of times to add a bunch of itterations from a mid to super high poly mesh for normal maps?