How difficult it is depends on how "thorough" the guy was that installed the 3" body lift was (he should have been SHOT for going along with it
). If he used heat to bend the transmission shifter then it may look pretty odd once the 3" has been reduced. He probably also had to extend the fuel and vent lines. How he did that is also going to affect how hard this job will be. If he installed a transfer case shifter bracket to level it up, that may have to be removed too. That bracket fixes the problem where the transfer case shifter bracket is uneven due to the side of it bolted to the tub which has been lifted up 3". Good luck since it may not be real easy, but getting rid of that 3" BL will be worth whatever effort it takes.