Lotsa opinions on the best way to lower them. Shorter shocks in the rear and drop it the same amount using a progressive or race tech lowering kit in the front, is the way I'd choose.
Are you sure that it has NOT been lowered already? Need to check dimensions against the specs in the Owners manual BEFORE you spend a bunch of money.
Then, does it have air shocks on the back? If so, check the number on the side of the shock to see if it is the original or the lowered one. If original, you can get about 3/4"-1 in off the back with the lowered HD air shocks. Match the front with the HD lowering kit. Not sure if that bike has the cartridge on the left or not. If it does, you might consider changing out the front assy for the '06+ version since you will probably have to rebuild the front end shortly anyway. Get the lowering kit when you do that and lower them before you put them on the bike.