What you have is a Freightliner Custom Chassis Corporation (FCCC)
XC chassis.
To get you started, I'll attach your FCCC feature and specification sheet for your particular coach.
Also attached is the maintenance manual that will pertain to the XC chassis at that time.
There's no tutorial on engine servicing procedures in the maintenance manual but somebody will nob doubt post that here for you. You can also do an online search for the CAT 3126E and I'm sure you'll find maintenance and service manuals to purchase or possibly for no charge (I haven't looked recently but as I mentioned, hopefully somebody here on the forum will give you a link or attach needed information).
A lot of information can be obtained by going to the FCCC website ...
go HERE or by calling their service number and giving them your VIN or chassis ID.
eta: here's a informative thread on changing the serpentine belt by a respected forum member ...if he doesn't respond in this thread, you can always try to PM him if you have questions. The access to the top of the engine is very easy as i had an '07 Meridian at one time where I went into the engine compartment numerous times to do things. The platform the mattress sits on has struts and will lift up and you'll see the engine cover:
Cat 3126e Broken Serpentine Belt
.