My action is very low at the 1-5th fret but very high at the 12th fret downwards. Wondering if I would fix the high action by adjusting the truss rod or the action at the bridge. Asking because the screws to adjust it at the bridge are f**ked and I cant check myself without buying a new one.

From your description is sounds as if the neck might be too straight. Check the neck relief - if you press down the bass string at the 1st and heel frets, there should be a gap about the thickness of a business card between the crown of the 6th fret and the bottom of the string.

EDIT I forgot to say that if you increase the relief, you will need to lower the bridge to get the action back down.
Last edited by Tony Done at Apr 8, 2017,