You will have to draw the systems by hand. Some units use the books while others use 11x18 paper stored in a binder. Since you are joining an establishment steeped in tradition, you will get to enjoy this painstaking exercise in attention to detail just as many stokers and members of the engineering department did before you.
I have seen drawings created through CAD programs but they were used for reference or as a rough draft to assist with layout. Creating drawings with a program would result in cleaner and easier to follow diagrams but it is far too easy for someone to copy the drawings and call them their own. Plagarism is thoroughly frowned upon and can result in administrative actions.
The idea is to research the system to understand how it works then trace out the pipes and draw a rough draft. Then you get to redraw the system neat and clean. Every drawing of the same system should look slightly different. This allows each person to become familiar of how the system works and the location of critical components. There may be times that you will have to quickly operate a valve under stressful conditions. Most of the time poeple will find drawings and just copy them... not cool but it happens. One of my drawings ended up on the Training PO's desk... it was photocopied and the name was changed. The lesson to learn there is that you need to keep your drawings locked up.
I haven't heard of the term "P&ID" before. I know that one of the drawings is called PG&D which stands for Power Generation and Distribution. It is one of the easier ones.
I just discussed this issue with a few Stokers at the Naval Engineering School and
What he said, apart from leaving us hanging with his last sentence.
Do your self a favour. When starting a system sketch, don't rely on your mess mates drawing as a guide. Chances are, it may be wrong. So don't copy it. Because when you're asked to reproduce it nice and neat on a whiteboard during a certification board or when your EOOW or Training PO asks cause he's interested in your professional development, you won't look like a plagiarizing idiot.
So get a flash light, a couple of pencils and drawing pad, get below the plates, and get sketchin'