Bro, just some suggestions to get started:
i) Train your ear to pick out the basslines - metal is great but it can be hard - Jason Newsted was often mixed right out of it, with exceptions and he worked hard to get himself heard. Suggest you stomach some other genres like pop and 60s rock and roll, through to NuMetal and straight up rock to expose yourself to as much of the lines, beats and styles. If you get bored with your exploration, by all means go back to your favourite bands time and again.
2) might have missed you mentioning this but join up with a band - just go for it and jam and pick some musicians both at and ahead of your level to reference your progress and keep it fun. Yeah you can do your favourite songs, but also find time to work with the drummer. You and him or her have to LOCK tighter than SuperGlue!
3) tabs are great, and agree with response to break down songs section by section. If you've never touched the bass, at least learn the notes on the fretboard as you practise so you can get more familiar. You will find runs and chord patterns that you enjoy playing - remember to hold on to those and practice them whenever you find the going tough - helps you remember, builds up hand strength, timing and feel, and your ear for the notes.
need more advice though
