Since you are sounding very hesitant, I would do as another poster recommended and help him find someone who does memory quilts on a regular basis.
If you are really interested in doing it, then start by deciding on an hourly rate that you feel is fair - and compute how many hours it will take you for each task - then get the estimate from the long-armer and add those, then add the time in for binding - and pad it with a few hours in case things go screwy - you can always refund unused hours if you decide that you overestimated by more than you are comfortable.
It sounds like a neat project, but not one that I would be comfortable doing personally.
Cheers, K