Don't you love the choice game?

Brakes, that'd be an easy just do it yourself item. Do yourself a favor and go OEM parts, saving a few dollars using the "parts" you can purchase local economy is a roll of the dice. My S60 was down right scary in the rain, the previous owner had used the 'take your pick' brand from one of the major chains for sure. With OEM on all four corners of the car the only nuisance is brake dust but the car stops ridiculously fast from highway speeds, tasca parts was decently priced for my OEM rotors and pads. Fuel filter will likely require under car access, something I am always weary of even with redundant jack stands....I am just paranoid.

I'd farm out the rest though unless you are confident shade-tree do it yourself.

Spending low cash on another used car is a gamble as you aware, something in the 4k corridor who knows what you are getting into. If it were me and it was a car for my kids I would invest into what you have....a very well built machine with a lot of life left in it.

As far as a Kia; I'd rather trust the safety of my family in a 2 generations previous Volvo than a Kia. Sorry if that is harsh and is not meant to insult anyone who owns a Kia.

Good luck with the decision process!