EAD
I did my wife's EAD myself and it came in 45 days early this year. The only document I sent was
1. I 765
2. copy of latest 1-94
3. 2 photos
4. Copy of I-485 receit
5. Check for requisite fee
6. A covering letter requesting an early action
This year I applied for my EAD and got a notice of action to redo the photos. Did it and sent again to INS. In the meantime, I got my GC approved. I have now applied for refund of the fees EAD and AP fees. Not sure INS policy allow refund, waiting for the check. If anyone got such a refund, I would welcome their comment.
If your wife has already used her EAD earlier, there is a possibility that her H4 status is invalidated and you may need to get extension of EAD for her to remain in status.
EAD's against employment based 485 is usually done at Service Centers. Check with your local INS office, you may be lucky to get it done at there.
If you have to spend, I would suggest you do it yourself, you can save a lot of money.
Remember, am not a pundit in these matters, take decision on your own judgement or good counsel.