Since the engine was running rough, I'd first suspect the torque converter,
rather than the transmission. When in park, does the engine run smoothly?
Do you get any clicking or other noise when you select drive or reverse? If
there's no action at all, either the torque converter has failed, or the
trans primary pump (the one that causes the clutches to select) has given
up.

Whatever the cause, the trans likely has to come off the engine to be
inspected, and to get at the torque converter.

First step is to get it evaluated by a professional. Don't take an immediate
"the tran$mi$$ion has to be rebuilt" as the diagnosis. Ask questions. A
reputable shop will know how to evaluate the torque converter without taking
it all out.

Be aware that it may well be significantly cheaper to buy another running
and shifting 93 than to fix yours.