Family Based GC - Attorney vs self?

[hurryguy]

I am currently in H1 B visa (Work based visa) and have been working in united states for a private software firm since 2007. They have applied for my GC under EB-3 and I-140 is approved and waiting for my priority date (which will not happen in the near future since its EB-3).

I got married to US citizen 2 weeks ago. I am planning to apply for Family based GC. How complex is it to file family based GC of our own instead of hiring an attorney? Also, do you know what is the reasonable attorney fee for the process?