GC process consists of 3 stages:
1. Labor Certification in PERM process (DOL certifies that no US workers are available for the specific job): 3 or more months of advertising, plus processing time (6 months estimated). The date of filing the labor certification is the priority date.
2. I-140 (immigrant petition): can take about a year.
3. I-485 (adjustment of status): the priority date has to be current to file for I-1485. Processing time depends of the background and name check. Typically it can take about 6 months to a year. But if the priority date is retrogressed or visa number is unavailable the case cannot be approved.
About the fees, there are USCIS fees and Lawyer fees. It may take somewhere between 5 to 6K (approx). You can change jobs if I-485 is pending for more than 6 months. If you change jobs after I-140 approval, then you can carry over the priority date while applying for the GC with new employer.
