The intake form is useful not just as a checklist of what you received and what you need to do, but also as documentation of the condition of the system, etc. I believe there's at least one member here who's had legal issues where someone came back claiming to have dropped off something very different from what was actually received.
The outtake form is documentation of what you did and what items have been returned to the client (e.g. returning the old HD to them?). One of the other recent threads talked about medical office "face sheets" with the 4-6 columns of small-print procedures - you could do something similar to that for your in-process worksheet/outtake and just check off the various things you've done that you'd charge for.
As far as keeping track of forms, the simplest thing I can suggest is Microsoft's Office Lens (or OneNote), at least on Android. It'll auto-crop to the page size (best if it's on a dark background), and you can save as pictures, PDFs, to OneDrive, etc. The camera on the phone is always with you.
