Definitely trade in broken ships as opposed to trying to fix them up. The material cost to get everything functioning again is massive and will take you approximately forever. You're better off trading in for a ship with slightly less inventory capacity than trying to restore a dozen or two broken slots.
If you're having issues with making money, equip 3 S-Class Scanner upgrades on your multi-tool. They increase the credits from scanning animals and plants by 6,000 - 9,999%, so with 3 of them active, you'll be earning hundreds of thousands of credits for each animal you scan. There are additional ways to make lots of money later, but that will suffice through the early game to keep things affordable.
I found a new multi-tool and an S-Class scanner upgrade after I jumped. Definitely excited to start making a bit more $$$
I saw something on reddit where a guy found an item worth like 8mil units. How do you go about finding stuff like that? Are there spots on the map that I should be investigating? Certain landmarks or icons or whatever that might yield better treasures to sell?