My shifter is loose and will move from low to neutral to high with very little resistance. I still have to press brake pedal to get it out of park but otherwise it is very sloppy. Looked at illustration and can't really tell where the detent is located and what makes it work. Any help appreciated.

 

You'll just have to tear into the outer shift quadrant and find out what's wrong. Could be anything from just needing to be cleaned up and greased,to worn, rusted parts from water intrusion. These models were bad on this even though the cover had a gasket. Here's some pics on what others have done. Hard to Shift 700 Sportsman 2004 - Polaris ATV Forum

 

It feels as if the detent has failed. any idea where the detent is located...possibly in the cover. The bike has not been submerged in water or out in the rain so I think we can eliminate that.

 

Doesn't have to be in the rain to get all corroded inside as I've found out over the years. The spring under the detent pawl could be rusted out/slipped out place,or the detent gear could be the problem causing the sloppiness. Items #4,63,and 65 on this parts break down.Dirt Cheap Yamaha, Polaris, Suzuki & Kawasaki OEM Parts & Accessories – Cycle Parts Warehouse