Good for you to get the POH/AFM in order. While only the current W&B is required, most keep all the old ones (marked superseded with the date). This allows going back and rechecking for math errors (which are not uncommon). However, if you reweigh the aircraft, there is no value in the old W&B calculations.
It's not a bad idea to update the equipment list to agree with what is currently installed, but I would not try to recreate all the additions and deletions over time. Also, a lot of equipment comes with an Aircraft Flight Manual Supplement (AFMS) that is legally required to be added to the POH/AFM and you should collect any of those that are missing.
When you get this done, if there is not a current AD and service document history, it would be good to comb through the logbooks and create one. This way you and your maintainer can easily verify compliance with ADs and service bulletins/instructions.
There also should be an airplane file where you keep other documents such as invoices and wiring diagrams and 337s and the like.
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