Welcome to the forums. Yeah, I think the Foreman was designed to be a little more "work" oriented than the Rancher, but that doesn't mean the Rancher can't be used as a work machine. Both are great ATVs.
The 2000-2003 Rancher 350s are exactly the same and the 2004-2006 Rancher 350s are exactly the same. The only difference in the 350 Ranchers, is that the body style was changed on the 2004-2006 Rancher 350s. Let me add that there is one slight difference between the 2000-2002 Rancher ES and the 2003 Rancher ES and that is in the computer system. The 2003-up Rancher has the ability to store trouble codes when the ESP system senses a shifting problem. The 2000-2002 Ranchers didn't have the ability to store and display trouble codes.
Most 4-wheeler problems are caused by a loose nut connecting the handlebars and the seat!!
You only need two tools in life -- WD-40 and duct tape. If it doesn't move and should, use the WD-40. If it shouldn't move and does, use the duct tape.