Ive never replaced a tractor clutch, but i would think it would be a good idea to make some chocks out of woood to wedge between the front axle and tractor bottom to keep the front from pivoting left or right.
You can search thru the forums for (splitting tractor) and get alot of info that way. I do know you will need some jack stands to support at least one half of the tractor and the other half you will have to use a floor jack with wheels so you can roll it away from the other half.
Hope this is helpfull, and good luck.