First time cat 631C owner

So I ended up with a older cat 631C scraper. Can someone tell me where to find the ser #. I have never had one if these or driven one until yesterday. I need to get a few things for it. And a book also.

Overall it seams to run and work fine, but I do have a few question about it. The brakes don't work(seems like most are that way) so when I push in the red airbrake button, it pops back out after 20 seconds or so. it does pump air and can here boosters when stepping on/off the pedal. normally the reason for bad brakes is wore out shoes or some easier to fix problem? I don't really need to have them working just sort of curios about them.

The hold trans pedal, not sure what that does. and the diff lock pedal are sitting on the floor. they are supposed to pop up so they can be pushed down to work? air operated or hyd?

I have around 15yrs experience with excavators and big and small dozer, track loaders, trucks and 20yd pull scrapers. None with self propelled scrapers. I have been reading some of the threads about them but I am open to any tips or things not to do while operating from some of you guys that have some experience on these machines.

Thanks in advance. Steve

First time cat 631C owner