transmission no reverse

I have a 97 blazer 4wd , just lost reverse and the forword gears are reving real high before it shifts and no od. I searched the threads and think it is the sun shell reaction gear. My question is how hard is it to fix. is there other upgrades and manuals I should know about? I have very good mechanical ability but have never done a transmission. Thanks for any help

Sunshell is gone.

I would not attempt this replacement on your own, get a good tranny shop to fix it, it won't be as much as a total rebuild.

Defiently sounds like sunshell. They are really not that hard to rebuild. I have done my trans in my '95 Jimmy, and have done a few 700R4's previously. The internals are exactly the same as the 700R4's, the major difference being the valve body. It took me a good two weeks on and off for the Jimmy's(had to work) to get it rebuilt and installed again. I upgraded the internals, bought a better, stronger sunshell. Upgraded the clutches inside, and did all the updates to the valvebody, all gaskets, rubber, all bushings, etc, etc. If you decide to tackle it, get a good manual, take your time, and you'll be fine.