Transmission slipping no reverse

You need to check the oil level first and check that the oil is not burnt. If it smells burnt and is very dark in color, this is a sure sign of internal slipping of the clutch packs. If so, further detailed inspection will be needed first hand by a transmission tech to determine the level of damage done so far. The more it is driven in this condition the more damage will be done.

You need to inspect inspect clutch pack, trouble is once stripped you are best served doing a full re build, but that is a very complex job, just doing what looks worn may not be enough, and with out actually inspecting the transmission first hand I have no idea as to what is worn and damaged. Often pictures are not enough as you really do need to inspect this first hand. I would be talking to your local transmission work shop, and make sure that you fully understand what you are getting into and that you have all the correct tooling and relevant information to do the job. One small error in diagnosis or assembly and you will be stripping it out again and starting over from scratch.