Your undergrad degree doesn't matter whatsoever, but I would advise you to take something that will hone your analytic and writing skills.
Then you take the LSAT and apply to law schools.
Then you pass the bar and work at a firm that does litigation. If you are talented and work hard, you can have a good career. Top third of the graduates are still being hired out of law schools.
This depends on the laws in your state, and the type of claim you are presenting. I assume you are asking the question in the context of a liability claim. If this pertains to auto liability, it would be important to apply whatever the laws are in your state. For example, if you live in a No-Fault state, your right to bring an injury claim is limited.
Insurance policies make a distinction between “personal injury” and “bodily injury.” They are not the same. A bodily injury pertains to a physical injury to your body. A personal injury pertains to things like false arrest, slander, etc. (Plaintiff attorneys frequently use the term “personal injury” to represent both.)
With respect to your injury claim, you must prove (1.) liability, and (2.) damages.
To prove you sustained an injury, you will need documentation of your injury from your medical provider or doctor. And it helps if you have objective findings as well within the medical records, which means your injury is more than just you making subjective complaints about pain.