Need Advice on Salt Water Generator purchase & conversion

Hi,
We have a 20,000 gallon inground vinyl lined pool. We have been using Baquacil but have found it to be too expensive and not without problems. We will be opening our pool in late May and want to buy a salt water generator.

We are looking for advice on the best brands of salt water generators. Anthing special we should know? Is buying one rated for a larger pool a good idea, or just a waste of money?

Would we have to have the filter running 24/7 with a salt water generator?

Also, any advice on converting the pool from Baquacil would be greatly appreciated. Right now the water level is below the jets. We thought we could just completely empty the pool and then refill it when we get the salt water generator. However, we have been advised that even for a short period of time, draining the pool completely would cause shrinkage to the vinyl liner.

Sorry for all the questions, but as you can see, we need help :D Thanks in advance