I am not sure how specific Bill Bulfer is with regard to dispays (EFIS/MAP vs PFD/NF). I am not sure an FMS manual is the way to go. The classics and NGs both use essentially the same software (U10.7 for now, U10.8A should be out in the spring). There are some FMS capabilities that the NG has that the CLs do not (TOGA to LNAV, arming LNAV for takeoff). The NG uses weight based maneuvering speeds rather than "block speeds".
Most differences are not big, but there are quite a few.
The FMC's are NOT the same. The -300's(Ex-UAL)/-800's I flew at ATA were similar, as far as updates, but there were differences. Not all classics have U10. I flew with Cayman and there's was lower. Keypad functionality is different between the two, as well. I've used the Bulfer books. They're good. ALPA national is over it, you should be too.