Just bought a M600 last week. (Came with a Case D100 backhoe). Just joined this site today. Already bought service, parts and owners manual. Anyway, I have lots of rust in the fuel tank. Looks like it coats the walls - looked at it with flashlight. I looked through all my manuals, and I looked online, but I can't find much info. Is the tank removable, or welded in? Any suggestions on how to get it cleaned out would be appreciated. Thanks.