hello i bought my car w/ 32k mileage to find out that the 30k service wasn't done. i'm looking to change the oil and the fluids and do a buncha other maintenance on it

air filter: i'm looking for a K&N drop-in, will this be a good idea? i'm doing it mainly for the fact that i won't have to keep replacing it, but i heard "higher flowing" intakes are NO GOOD for our cars?

brake fluid: what do you recommend and how much of it does our car take? also where can i find it? i just came from a kragen and they didn't have crap

engine oil: this is a big dilemma. i don't know if the previous owner used synthetic or not so i'm not sure what i should use, the car already has 32k on it now, is there any way to tell? i've read Amsoil or Mobil 1 are the way to go (if i can use synthetic)?

oil filter: what do you recommend? will i be okay w/ PurOne or do i need the Subaru OEM?

spark plugs: what kind and where can i get order some? i'm only expecting UP/TBE/EM in the distant future

transmission fluid: what do you recommend and how much? also where from?

rear differential fluid: what do you recommend and how much? also where from?

thanks all, i'm just trying to get my car running in the best condition it can, i appreciate the help