Depending on where you are, I can offer two choices. There is a shop in Ventura or Van Nuys (?) area that gets a LOT of Montero business. I cannot for the life of me remember the name of the shop, but on Facebook, look up "WM F Coleman" who works there, and is the administrator for the SoCal Mitsubishi Montero group.
Second Option, if you are in Orange County, and have patience and want to learn, I'd be willing to help you. I rebuilt one 3.5L successfully, and its still on the road! I am a amateur who has watched a lot of YouTube videos and collected a fair number of Harbor Freight tools, including an Engine Hoist