Not a huge 4t65e expert but in dealing with my own the not wanting to shift into overdrive sounds like a worn 4th clutch hub. Which is strange since the later years had the hardened shaft to eliminate this issue.

Never had one shudder but that symptom to me sounds like a torque converter lockup issue. On a full rebuild you should have a new/reman torque converter in it. Hopefully they didn't reinstall your old one.