Axle Shaft Question
So I took my truck to a mechanic that my Aunt knows for a really bad drum brake squeak. It's a 97 2.3l 2wd. Found out that a spring came off the brake and was scratching metal on metal. He replaced the tensioner cable for $35. Loan behold when we checked the other side, passenger side, it was covered in axle grease. He then proceeded to show me what could be the problem. He took me over to an old axle shaft that he had and showed me the groove that a wheel bearing can make on the axle shaft.
Now I have little to no knowledge of how to inspect the axle shaft to see if the shaft needs replacing or if it's just a wheel bearing or the oil seal that needs replacing. How can I check to see if I need to get a new axle or if it's just a bad wheel bearing or oil seal? I really want to do this myself if that's possible for an absolute beginner. I have done minor jobs with my truck like tune-ups, pinion seal replacement, almost did the ball joints. Would I be able to do this myself and would I need special tools?