Yes, I have done it as well. Have a spreadsheet on the CRX with all the info you talked about including milage, service, mods, how much they all cost and worse of all, a running total of what my hobby has cost in real dollars.
Got a sheet on the DD, a 94 Integra GSR, also. I still have to start a sheet for my newfound baby, a 74 260.
I also have service manuals, mod info, suppliers catalogues, and a spreadsheet devoted to turbo sizing. Plugin data and it gives you points to plot on compressor maps.
In short, yeah me too.
chris