Shoulder Impingement / Overbuilt Trapezius?

[Todd Richards]

It's taken me a while to switch back to CrossFit after sustaining some injuries that kept me out of the gym for a few months a few years ago. Once I did manage to get back into working out, I got back into the same old routine of just lifting and forgetting to stretch. This went on for several years. Recently, a Level I instructor convinced my local gyms to allow CrossFit on their premises and I am picking it back up. However, I have major mobility and flexibility issues. One of the most annoying problems is not being able to achieve the proper lockout on the overhead press because of what I can only surmise is extremely overbuilt traps or tight lats. I am unable to get the bar above and rear of my head into a locked position. My tightness and mobility restriction seems to come from my traps not allowing me into a full extension. Does anyone have any recommendation on corrective exercises to improve my lockout and combat tight lats and traps?

Any help would be greatly appreciated!