Van serviced (105K)and new motor mount. Trans. now leaks, did mechanics cause? on 2000 Honda Odyssey

Van NEVER had any leaks, serviced it regularly oil/fluids etc. Now at 174,000K so took in as it sounded a little off figured it was time for a timing belt and they did the 105K plus a few extras like water pump, valve adj/gaskets. It now has a substantial leak in the teansmission and they want $1200. I feel like they caused this problem but they say no because it is "behind" where they were working. I feel trapped and taken advantage of. If a engine and transmission work together, and a motor mount is broken and timing service is done, can this cause the transmission to leak? Also, if the multipoint inspection shows that all was checked and with no problems, now they say this is a substantial leak and they do not recommend driving it.

Asked by for the 2000 Honda Odyssey
Any visible damage under the car like a jacking device may have been misplaced on the transmission? Get another 'private' shop to hoist it and look. Find out where the leak is! Were all mounts replaced?
To my knowledge, only the one visible on the left (which looks like it would have needed to be taken off to do timing belt service anyway)?
I requested they place all used parts in a box. One mount and a couple of belts, the old water pump and the adjustor were all that was there.
Honestly I do not feel like they did a true multipoint inspection. Nor did they replace the cabin air filter like I asked (it has never been replaced)or at least they did not leave me the old one.
Doesn't answer my question. Need to get it looked at by another shop!