I assume you mean either the Severe Duty model or the Classic XL, In the glove compartment, on the bottom or on the door, there should be a sticker... it'll have the VIN, rear end gear ratio, transmission model, axle specs, etc.
Try a Freightliner service department.
Remove the screws, pull out with a trim puller.
In order to find instructions on how to read the fault codes of a 2000 Freightliner FLD 112 with a C12 engine you should go to heavydutypowertrain.com where they have an extensive selection of instructional material including how-to videos.
Try replacing the speedometer switch on the transmission.. that's probably your culprit.
It comes with whatever sized tanks the orignal purchaser ordered it with.
You won't find one without the make and model of the engine. Or, you contact a Freightliner dealership with the last 8 digits of your VIN, and they can tell you the part number.
Hook up a laptop with the appropriate software to read Cat fault codes.
It is the right arrow: p->fld means (*p).fld
For example: struct { int fld; } v[2]; v[0].fld = 1;
Depends on which model Freightliner you have. If you have an FLD (120 or 132), you'll have to unscrew the panels they're mounted into in order to access them. It may involve removing multiple interior panels which overlap each other. If it's a Century Class, it should be much easier.. a lot of the times, the only thing holding those panels in place is the seal around the doors.
a quart is larger.
It's a simple remove and replace, BUT... you'll want to get a shop to recover your refrigerant first.. discharging it into the atmosphere is both dangerous and illegal. You'll also need to replace the receiver-drier any time you open up that system and expose it to atmospheric air.