I've a Brookstone suction pump. It's kinda slow. Think they offer a container linked to a vacuum pump that would be much faster. Think it's about $40. You could probably make one yourself using one of those hand vacuum pumps like I use to suck brake fluid out of the master cylinders for changing once/year. Just run it through a tank between your engine sump and suction pump. It'll take a few pumps to get the vacuum drawn, but it'll then suck pretty good with a stiff line into the sump under oil.
You could probably use one of those pumps that you put on your electric drill. You just need a stiff, skinny suction line to go down the dipstick hole. Actually, for your tractor, it won't need to be too skinny, just stiff so it doesn't curl at the bottom of the sump.
The Mercedes mechanics at the local dealership said this is how they change the oil in their clients' cars now, by suction pump. It's a lot easier on cars nowadays that have enclosures underneath the engine compartment, like all Benzes, Buicks, etc. have.
Ralph