Isn't the repair menu the only way to fix wear&tear? If so, I'd say its worth checking out from time to time. And "Ouch" on the Clipper thing.
If by wear and tear you mean your paint, no, I believe it gets auto repaired (oddly only ever to 99%, which probably sparked your question)
There's also that other repair hull function at the top right of th repair menu that seems bugged, I can usually still spend money even though the ship is at 100%.
Hold out for a Cobra, just keep doing what you're doing. You'll get a big jump in Cargo space and firepower. It's worth the wait.
I was actually wondering this too, do I need a Cargo Scanner? I went to one and it said "buying top 10 trending ... " or something like that. But not sure what it meant.
It's certainly useful to have, but you don't
need a cargo scanner, you can just keep doing perfomance enhancers for now, you don't need to rescan them every time. I don't know when or how they change their preferred commodity, I believe it's either a global setting or system wide. But I haven't seen the demand change within one system over a few days.
What is the next hauling/trade ship?
As flyingpiranha said, you should prob keep the hauler until you get a cobra. Cobra has 40 cargo (with shield) and that'll pretty much double your income. After that the Type 6, then Type 7 then either Clipper, or you sit through all the way to python. T9 is a somewhat qustionable upgrade, as your jump range is really low, but apparently that thing rocks for "seeking luxuries" as you don't have to jump at all.
This guide is good in general, and the trading portion pretty much gets you through the motions step by step:
https://forums.frontier.co.uk/showthread.php?t=80291