I am very familiar with the WMD program as I was in the National Guard for 10 years before my direct commission on active duty. The threshold question I would ask is whether your injuries were caused by/incurred during the execution of these hazardous duties or during an exercise. Understand that just being in a high speed unit does not make the connection between your disabilities and a combat related finding. Imagine an Army Ranger or AF Para-rescue troop who injures themselves during normal physical training. This would not count as combat related. However, if they were rappelling down a building and were injured, then it is a likely argument that the injuries are combat related.
To answer your questions, you do not need to hire a lawyer. Depending on the facts of your case (especially if it is a close call), it may make sense to do so. The PEB makes the initial determination regarding combat related findings.
Hope this helped. Best of luck in getting a good outcome!