EB3 Questions

Hi all, I have recently have my I140 approved and my PD will be current from March 1st. Then I can file for I485, EAC,and AP. My employers, where I had completed my OPT are filing through their lawyers. But, they have not really told me exactly how long I may have to work for them. I remember I asked them last year and they said that they want to finish the filing first. This is actually their first time of doing it. It's small county hospital at the middle of nowhere, about 2-3 hours away from the closest big city.

Anyway,my questions are, for those of you that have gone thru similar process, how many years am I looking at putting in for this hospital? I was looking at nothing less than 1-3 years max. Honestly, I wouldn't want to live more than a year in that county. I only worked their because I didn't have anywhere else for my OPT.

I also intend to get a personal lawyer when the time for signing the contract reaches. Is this a good idea?

And lastly, how long does it take to get the I485, AP, and EAC approved?

Feel free to drop your suggestions. Thank you!