B7300 PTO won't disengage

I was operating a B7300 yesterday with a tiller implement attached when the tiller froze with a jolt and engine stalled. As far as I could tell, a rock got jammed in there and caused the stall.
I lifted the tiller off the ground and restarted the engine fine, but now the PTO will not disengage.
The lever on the left hand side next to the seat has an option for 540 by moving it back and one for 900 by moving it forward and then a neutral in the middle. This lever will now only slide between the 900 and the neutral section and will not got down to 540. Even when sliding to 900, you don't get that little click/jolt like you can feel it engage something as it used to.
The lever still has to be in the neutral position and the clutch depressed to get the tractor to start so I know it's depressing the electrical pins correctly.
The PTO just turns constantly now even with the clutch depressed. The only way to get it to stop is to turn off the tractor.
HELP PLEASE!
Unfortunately, this is my father-in-law's machine that I was borrowing and I don't want to be disowned from the family.

Just in case someone reads this looking for a solution.

I read a post while looking for a solution that said it might be the pto shift fork. I had no idea what this meant but the person said if you remove the mid pto then you can look up inside and see.
The mid pto is right under the seat with four bolts that are removed. FYI...all transmission fluid will come out when you take this off so drain the fluid first. (there is a dran plug on the left side of the mid pto, and two more drain plugs in the back kind of by each wheel)
When I removed the mid pto, I found some pieces of metal in there and was able to look up in and see what a pto shift fork is. Essentially it's a C shaped piece of metal that moves forward or backward when you move your pto lever from 540 to neutral or to 950. With it broken, it will either not move at all or it will move forward and backward without catching to engage or disengage the gears.
I was able to reach my finger in there and push it so it disengaged, but after running the tractor for a few seconds, it slipped back in and re-engaged the pto.
Anyway, I'm not going to open up the transmission to get at that pto shift fork, so I'll take it to the dealer.
One problem I have now is that after draining the fluid, I obviously had to refill it again and after doing so, my front loader and rear 3 point don't work at all.
Ill check pump, filter, screens, and try to get air out like people suggest and see if it works. I used gray gasket maker from local auto parts store when I put the mid pto back on and maybe didn't get a good seal.
Anyway, hope this helps somebody.