Hard shift and front diff leak on 2004 Yukon

Hi there, New to this forum as of today, but wanted to get some others opinions rather than my dealerships. I bought an 04 Yukon ST with about 66k miles on it. At about 75k miles I started experiencing a very "minor" hard shift from 2nd to 3rd gear. Took it to the dealer who checked the tranny fluid and test drove. Said it was most likely something they'd have to open the transmission to clean/replace some valve in there. They mentioned it was not detrimental (spelling) to the transmission, but would be around $800 to do? Anybody have any other ideas that might save a few bucks? This was only the tip of the iceburg. In addition to that, while they were changing the oil, they mentioned the front diff seals were leaking. I've heard in the past that it's typical for them to weep, and when questioning them, they stated they were beyond weeping. I've never had any differential fluid on the driveway, and didn't notice much underneath other than some oily substance build-up with some grit on it. To get it over with, I told them to go ahead and replace both front diff. seals for about $400. Went to pick the vehicle up, and found out that they were only able to replace the front right axle seal. They said they weren't able to replace the front left because the axle was seized in the differential case, and it was going to cost about 2k to fix as it would take an entirely new differential case to resolve the issue with the axle being seized?......................So now between the hard shift and leaky diff. seal, I'm looking at $2800. Needless to say, I'm pretty bummed out, as that's alot of cash to be dishing out that I don't have right now, especially this time of year!!! Any experts out there with ideas or opinions? It did look as though they tried pretty hard to knock it out, as I could see a few pry marks, (or hammer hits) on the case. They said they tried everything, and didn't think they could get it out without doing serious damage!!! Thanks in advance for any thoughts!!

Anyone??

It might be your Rear U-Joints that are causing the hard shift..have you had them checked out before? Mine was just having the same problem last week and it turned out to be the U-Joints in the rear.