It appears the loader will have to come off. to replace the clutch, the tractor has to literally be split (separated) at the bell housing. Engine half pulled forward, transmission half pulled back.
Was the clutch slipping prior to this happening ( did you notice you required that you needed to use lower and lower gears for it to pull itself for instance)? Does the pedal feel normal when you push down on it? I assume the tractor is in neutral (?), can you rock the tractor back and forth a little and get it to engage a gear? Or if it's in gear rock it and get it out of gear?
Just trying to get a better idea of what was going on leading up to the problem and if it may be something else.
TractorClutchesRUs - Tractor Clutches has served me well for clutches in the past and I believe they can reline your old one if they don't carry a replacement in stock. I'm sure they can supply a pilot and throw out bearing as well ( you may have to take the old ones out and measure them first though.).