Codes P0505 & P0325. Chk Eng lt on but car runs Great!

97 Altima GXE 5 speed. 86,393 original miles. (1 owner, 71 yo Man) Picked this bad boy up for 1800. Very clean in and out.

Light was on when I bought it. Car runs great, with no issues.
Had the codes checked at autozone. Codes were P0505, and P0325. Cleared the codes, and 4 days later, solid light came back on. Ran codes again, P0500, and P0325. Print out is as followed:

P0505
IAC circuit condition or idle speed higher/lower than expected
ECM has detected that the IAC counts are higher or lower than expected. The Engine speed is not in its expected range.
Probable Cause:
BB1: Vacuum Leak on engine
BB2: Dirty Throttle Body
BB3: IAC motor Defective
BB4: Poor Electrical Connection to the IAC Valve

P0325
Knock Sensor Condition
The powertrain control monitors the knock sensor signal for errors
Probable cause
BB1 Knock Sensor Defective
BB2 Check connector and wirinf to sensor
BB3 Engine mechanical condition-knock or rattle in engine
BB4 Low fuel pressure

Ok... The only common denominators is the fuel category. i.e dirty throttle body, and low fuel pressure..

There is no telling when the last tune up was done on this thing if any at all. I had the oil changed the day I bought it, and the light was still on.

Anything you guys suggest I do first? I've read several post about knock sensors and IAC valves, but not one that has the 2 listed together with my listed symtoms which are none to my knowledge. No mis firing,sputtering, stalling at low idle, nothing! Car runs fine, averaging 29.6 MPG on high way.

Any help with this would be great!
Thanks guys!