I also bought an Amigo with 60K+ miles that never had anything done to the transmission. On top of that the engine had a cracked head that caused it to overheat. Not sure how many time it had overheated before I got it, but the ATF was a black varnish and it did not want to shift. I changed the fluid and filter and things started looking better. Now I change the fluid about every 10, 000 miles. I found an easy way to do it at home. I bought a Fram Sure Drain plug assembly to replace the drain plug, I found it at Pet Boys for $10 ( http://rustysoffroad.com/article_framsuredrain.html ). I still pull the drain all the way off to drain the fluid. Then I put the plug back in and use a PLEWS LubiMatic Fluid Quart Pump to fill the pan through the bottom drain ( http://www.plews-edelmann.com/brochure.cfm?brochure=1916&location_id=2626 ). The vinyl hose on the pump fits tight in the center of the Fram drain adapter. With the top plug removed you can pump ATF up through the bottom until it starts to overflow out the top plug hole. Start the engine and shift through all the gears and put it back in neutral and finish filling the pan. When done you can just unscrew the drain adapter and screw on the cap seal without loosing any ATF. It takes about 15 minutes to change out the ATF with this equipment and no mess! You will need the Sure Drain SD-2, M14x1.5 .