To do an oil change see this http://www.mytractorforum.com/232-articles-drive-train/161413-how-do-oil-change-tuff-torq-k46-transaxle.html

To see how to repair the K46 see http://www.tractorbynet.com/forums/parts-repairs/164892-tufftorq-k46-repair-guide-pictures.html

To get a tractor with a better trans you will probably exceed $3500. I have a Deere X300 for 5 years with the K46 and first thing I did was drain the factory 10-30 oil and put in 5-50 Synthetic which will make it last much longer. It is a good trans - keep it clean and do not over work it and it should last. A rebuild looks easy for someone with average mechanical skills.

The K46 in this unit is a "sealed unit".. can you still change the oil??

It's only sealed if you don't take it apart:) See the oil change post above - you just take our the trans, remove the plug, turn it over and drain. Then refill with 5-50 Synthetic and put back in the tractor. Did mine in about 90 minutes (most time waiting for the oil to drain). 4 bolts and 3 clips to remove the K46. Most people do not see good results with just an oil change, but doesn't cost much as a try.

Explanation - sealed unit means the selling company will not service the unit, the cost of repairing by the company (lot of labor) exceeds the price of a new unit and they would rather put in a whole new unit. As the links above show it is serviceable by do it yourselfers (free labor) with just the cost of parts. The unit also does not have a drain plug or fill hole so they will not service even changing the oil, but it can be done with slightly more work.

Try the oil change, there have been several success stories just doing that. FWIW, there's a reason that Hydro (Hydraulic) trans have fans and fins, it's to dissapate heat. Heat breaks down the oil creating issues. If you can resurrect it, and by all means use the synthetic oil, it will buy you time to look around and make a "good" rather than a "gotta mow the grass three times a week right now" decision. :-)

Good luck,

Ev