Encoder motor (transmission)

[RoboProp]

My 99 Blazer wont shift into 4 wheel drive (hi or low). When I push the dashboard button/s, I hear a few clicks while the light is on and then nothing and the light returns to 2x4.
The dealer says the encoder motor is gone and needs to be replaced at a cost of $1000. I've looked in two (namebrand) manuals for an explanation of the device and its purpose but no mention can be found.
Only 71,000 Kms on vehicle and this seldom used (little snow in Vancouver) device is shot!
- Can a novice fix it?
- If replaced, should it be replaced with a superior (non-Chevy) product?
- Any recall notices anyone is aware of?

Thanks in advance.