All this boat seems to need is a tidy up and a cleaning
Run one of the marina's dollies alongside 'er and throw everything that is loose in the the boat into the dolly so you can see what you are doing. Take the dolly to the parking lot and throw everything into the trunk/boot. You can triage it later.
NOW you are ready to decide what you want to do to 'er!
In a 27-footer, wiring is simplicity itself. After all how many discrete circuits are there? Check all the wires visually where they connect to devices. If anything is dodgy, check the circuit for continuity and voltage loss with multimeter. You'll probably find that everything is good, and that anything that is not, is bad only because of a dodgy terminal that you can easily fix.
Lack of tidiness at the control/switch panel is another thing you expect to find in a boat with a messy interior. If you do find that, tidy up by using terminal blocks to facilitate leaving the actual wire runs in whatever places they have been concealed behind the ceilings and the furniture. Don't have a link handy, but not so long ago, someone here posted pics of an absolutely splendidly executed revamp of the wiring behind his control panel
When TP came to us, I installed terminal blocks adjacent to all devices so that disconnecting a device for servicing or replacement can be done without disturbing the actual wire runs. E.g for the side lights on the sides of the house a terminal block was install on the INside of the house under an access panel in the ceiling.
Something that dives me daft in too many boats is that cushions are often far too long. A cushion that runs the full length of a 6 foot 6 inches long settee/bunk with three top-loading stowage compartments under it should OBVIOUSLY be made in three 2-foot sections so you don't have to lift
the entire cushion to get into just one compartment.
By your pictures, the material used for your cushions is something that even a little domestic sewing machine
can handle. If it isn't, or if you want to change it for appearances sake, then use a decent upholstery velour that you can buy in any fabric
store. Making what is called "box-cushions' is really easy and since a domestic sewing machine
will do the job, you can even do it right on your dinette table. Sailrite
, a supplier of all the necessary clobber to do such a job, has excellent "how to" videos of every kind of sewing job.
But don't get involved in making modifications to the joiner work. That is a lengthy and difficult project
that will be more expensive than is warranted.