Welcome to the Forum and to RVing. Very sorry to hear about your father, ope you can enjoy his memory in his motorhome.
The headlight housing is likely an automotive one. Who made the chassis? Ford? GM? As an example the headlight housing for our previous rig, a 1997 Triple E on a Ford chassis came from a Ford Explorer. Hopefully you will get an answer here but if not take the rig to a Ford, Chevy etc dealer with a good parts man and they may recognise it.
As for the driver's seat, now is the time to upgrade! Auto wreckers will have a great selection of comfortable seats. Find one that you like an that will fit.
Here is a link that might help:
http://www.mhsrv.com/other-rvs-for-sale/mountain-high-rv/