Hi Keith, you are actually eligible for both the Montgomery GI Bill and the Post 9/11 GI Bill. I am assuming that you have used no GI Bill benefits yet, so if you switch to the Post 9/11 GI Bill, you will receive 36 months of education benefits, and you will have 15 years to use them from the time you left active duty.
If you remain on the Montgomery GI Bill, you receive 36 months of education benefits and you have 10 years to use them from the time you left active duty service. However, since you are eligible for both GI Bills, if you use your 36 months of Montgomery GI Bill benefits, you can also receive an additional 12 months of Post 9/11 GI Bill benefits, for a total of 48 months of benefits.
You are not eligible to transfer your GI Bill benefits to your spouse under either program. The transfer provision was added to the Post 9/11 GI Bill in August 2009, and to be eligible for the provision you would have had to have been on active duty 1 August 2009. The Montgomery GI Bill does not have a transfer provision.
You are eligible for the housing allowance while using the Post 9/11 GI Bill, and carrying more than a 1/2 course load of credit hours for a semester, and the classes have to be traditional classes, not online classes. You are also eligible for the Yellow Ribbon Program while using the Post 9/11 GI Bill.
I think that takes care of all of your questions, feel free to email in any others you might have, Good Luck!