Prime Runner contacts and modification work Options

[UmaroVI]

I'm not sure what the most appropriate way to handle this is and I'd like to hear what the consensus is. The situation:

I have a character who has the retirement benefit of a Prime Runner contact (that is someone else's prime runner, not mine, if that matters). That character is a very good mechanic who is capable of doing weapon and vehicle modifications.

I want to get a modification done.

Should I:

a) Use the standard SRM rules (Threshold hours in 8-hour days for weapons, Threshold x 3 for vehicles) to figure out how long it takes?
b) Figure out how long it takes the actual character?

Probably more importantly, what happens 100*(1-Loyalty/10)Y/hour he charges? Does it

i) Vanish into the AEther?
ii) Go to that character (as a prime runner, they can only play in prime runner missions, of course)?

If ii), I am assuming they also need to pay Lifestyle for time spent doing that.