ford transmission replacement

[sea ox]

Ok i have a 2005 F-350 mason dump with the 5.4 gas engine and auto trans. While towing my tractor around yesterday the transmission sprung a leak spraying fluid onto the exhaust. The trans still shifted fine, didn't overheat or make any strange noises or anything. The ford dealer says the transmission case is cracked. They want $2400-$2800 to replace the case and reuse the old parts with a warranty on the new parts. Or they could give me a oem ford rebuilt trans with a 3 year 75k warranty for $3,500. I also called around and am waiting on a price to replace with a re-man Jasper trans with 3 year 100k warranty. What should I do?