You will need to swap to a steel front diff, the mini spool won't work in the stock tracker front end. You will also need a 96+ extension shaft and passenger side CV.
It also puts a lot more stress on your drivetrain, as you will be dragging one of your tires around every time you turn. 4 wheel drive will be useless for driving on the road, you will be stuck with 3 wheel drive for most things.
I have driven Suzuki's with lockers in the back on ice/snow and have not have any problems. If your really worried about it spend the extra 100 on a locker instead of a spool in the back. Otherwise save up your cash and spend the 800 or so on putting an ARB in the back or spend 400 on a limited slip.