You are overthinking it. As an appliance operator, you get to check the bullet points.
Side A has two chains? Check
Side B has two chains? Check
Side A has X dBi of antenna gain? Check
Side B has X dBi of antenna gain? Check
(where X is equal or greater than what you already have installed.)
If you figured it out in 2006, you can handle it today. The hardware has gotten faster. The software has gotten easier. If you have problems during installation, ask us about those questions then.
I am not your vendor. If you call the place from which you are going to buy your hardware, they may take the time to give you a primer. I, like most people on this forum, am just a busy volunteer.
All searches come up with a billion advertisements. You can modify the search to focus in on the level of information you desire, once you know the key term. In this case, "mimo".
In honor of the book series:
A potentially less insulting way to say what the book series means: