Your chassis is probably by Freightliner. Look at the link below and click the tab on the right for "knowing your chassis". This is all I know about regarding the chassis without going to "camp freightliner" for the 2 day class (which I highly recommend).
Freightliner Motorhome Chassis ? XC-S Chassis
I think the 99 Holiday Rambler could have either a Cat or Cummins engine. You should be able to download the appropriate manual for your engine from the engine manufacturer's web site.
The Freightliner Chassis Owner's Club has some good tech info and chassis maintenance info on their site. Link below:
If you have more specific questions, just ask and someone here should be able to help.