If it slips more when warm and in manual mode I would expect a failed o-ring or destroyed A drum. My symptoms were similar to yours and my experience was a failed o-ring and bearing set.
I also ordered my kit from cascade transmission parts. No complaints.
However I decided to order from Cobra Transmission for everything else. They are great to work with and quick to reply. I recommend them 100%. Here's their info
John A.
BMW and MB Transfer Case Specialist
786-472-8500
[email protected]
RRPhil on Xoutpost is extremely resourceful when it comes to these transmissions. He's great help if you hit a snag in the rebuild.
I also recommend watching some of Gary Ferraro's 5HP24 tear down and rebuild videos on youtube. He's really thorough in his videos and quick to respond if you get a question on the 5HP24.
As far as tools go, you'll want to look into a generic clutch spring compressor. I picked one up from harbor freight and I was able to make it work for most things but I did have to get creative for one of the clutch springs. I used a 2x4 with several screws set to equal lengths around a circle the size of the clutch spring tongues. Not pretty but it worked. I don't think I needed any other special tools.
Good luck!