How does one come off of PPI's?

I got an email yesterday, and she needed help on coming off PPI's. Here's her case:

"I feel so bad. I truly feel that PPI's are wrecking my stomach. I started on Prilosec about 5 years ago for acid reflux. A few weeks after taking Prolosec I started getting really bad burning pain in my stomach. I had a GI do a full workup and found nothing. She switched me several times until Prevacid was able to help.

A couple years went by. The heartburn would come and go but I wouldn't notice the stomach burning pain as much. When the heartburn would come back, they would increase my dosage of Prevacid to where I was taking around 40mg twice a day. Then last April it all came back!! Lots of nausea, burning pain, etc. Ive had a big work up again and all they can find is gastritis.

I truly feel that the PPI's are really causing problems!! I have burning throughout the intestinal tract, trouble going to the bathroom (constipation), nausea and the burning pain is unrelentless. Can you suggest a good H2-blocker to switch to? I have tried Zantac and Pepcid and neither seem to help a lot."

Please post any suggestion/advice for her case