If you have no stand up game, you need to train stand up. MT is obviously a first choice due to the clinch and knee's that boxing doesnt have. But you need to guage your stand up skill after 1-2 years to see if your any good.
If your average on stand up you need to use the stand up game to take an opponent down where your more comfertable. You cant stand with a superior striker, you will be destroyed.
I would say 2 years for decent compertition you might want to enter. Of course you can enter underground MMA next week and get destroyed if you like. Just remember, if you get your arm broke due to bad reffering in a MMA match you may be screwed for a long time.