Using job offer contract in lieu of emplyment verification letter for filing I 485

[Scorpio811]

Hello,

My employer has asked me to sign a very restrictive contract extension as a condition for him filing I 485 on my behalf. He has signed it & it has information like the location, offered salary & other terms of employment.

My question is if can use the job contract extension offer sent by him to file my I 485 with my own lawyer? Will that be taken in lieu of the "Employment Verification Letter"? Will I need the employer's assistance in any stage to continue the GC process?

Any valuable inputs will be very much appreciated

Thanks,