#1
I bought my bass used and before that never actually played a bass before so Im not sure if this is normal. When I try to play higher notes, like 10th-12th fret on the G string, my bass sounds buzzy and almost doesnt produce the notes. Is this a problem with my setup or is it just generally harder to produce clean notes higher up on the bass guitar?
#2
ya, that's not normal. They should be just as easy to play as the lower frets. Prolly setup issues?
Try adding more delay.
#3
Set up problem, try checking the relief of your neck (by sighting down the fretboard, looking up from the bridge)

What you're looking for is an almost straight neck. With a slight bit of curve inward at the middle of the fretboard.

If it's too far inward turn your truss rod clockwise, this tightens it. If it's bent back, turn anticlockwise this loosens it.

If you're neck is good already or this doesn't solve the problem then try adjusting the string height at the bridge saddles. If this doesn't work you need fretwork and it gets more complicated.
Gear

Fender Geddy Lee Jazz
Fender MIA Precision
Musicman Bongo
Boss TU-2
EBS TD650
EBS ProLine 2x10 x 2