Once you receive a P3 profile, your med-board clock starts ticking. Depending on which blocks are checked on the profile, you will either go before the MMRB or the MEB within a few months. The MMRB will decide if you need to reclass and if you are eligible for another MOS, fit for duty to return to your current MOS, or recommend being seen by the MEB. Now, the MEB works like a whole new animal these days. Everything is changing and evolving constantly right now. When you go before the MEB, you will be determined fit for duty or unfit for duty. Look up your condition in AR 40-501 (standards for military medical fitness) if you need to.
If you are found unfit for duty, they will compute your disability rating and go from there. If you receive under 30% you will be medically chaptered and its basically like ETS'ing with some other benefits along with a lump sum severance. If you receive 30% or higher, you will be processed for medical retirement on either the TDRL (temporary disabled retired list) or the PDRL (permanent disabled retired list). TDRL is becoming very common these days when dealing with cases of TBI (traumatic brain injury) and PTSD. If your medical condition can be expected to improve in time, you will likely be put on the TDRL until they deem you need to be permanently retired.
Check out AR 635-200 and AR 40-501 though, you will probably find a lot of answers in there. Without knowing any medical conditions, its hard to know what you may be in store for in the future.
BTW, I'm not a subject matter expert by any means, talk to your Primary Care Provider about it all. I'm currently a squad leader in the Warrior Transition Battalion, so I deal with this stuff on a daily basis.
Also, Ft Carson has a WTU there correct? If you aren't in it already, maybe try and link up with a knowledgeable squad leader over there who might be able to answer some questions or look for the Ombudsman in the hospital on post to see if they can help you at all. Most of the Ombudsmen are all retired medical corps Sergeants Major, so they generally know their stuff.
Good luck with it all