couple of things: the 4BGE Maillemaker refers to is a great generator, I have owned several, and still have one mounted on a cart for a "portable" genset. But it has nothing in common with your RVQG (7HGJAB I assume). Your set has 2 magneto/coils, one for each cylinder,a triggered by magnets on flywheel.
to access them you have to remove genset from coach, lift engine-gen assembly off of base tray, turn on back to expose bottom of set. Then remove flywheel-belt cover to access magneto/coils. There is no ignition module, per se... the magnetos are controlled by main control module. $50 is ok price for coils, the main control board is $400+, depending on spec of genset. The hydraulic lift table is a very useful item, and you need some lifting equipment or couple strong friends to pick up the engine/gen assembly up from the base tray.
I would like to know the fault code the gen is giving you when it shuts off.
I have surveyed a number of Cummins/Onan dealers in SE US, they typically have labor rate of $150-160 hr
R&R of set from Tiffin should require 2-3 hrs at most, replacing coils, and drive belt while "in there" and bench test run about 3-4 hrs in a well equipped shop that has experience working on these sets
