If you buy just one thing, I recommend the CT CD.
Otherwise, I recommend exactly what Aramis recommends.
I've been running MGT with CT material since playtest of MGT. I pretty well convert on the fly, though important ships usually get converted ahead of time, and I at least look at important characters and their equipment ahead of time in case of the need for tweaks.
Characters change very little, weapons and combat are different enough to need conversion, but once you get used to it you can call it on the fly. Key tasks might be handled differently between CT and MGT, but once you're used to MGT you can call it on the fly. CT ooften specifies them as a sort of one-off rule, that's enough to get a feel for how tough it should be, which lets you convert to a standard MGT task check.
For the first couple of adventures I ran under MGT I went combat-light--only one gunfight in the second adventure. The first (Shadows) I just had to be up on the task system, the second (one of my own) I had had a chance to run through some combat scenarios solo with the MGT rules so it went smoothly when I ran the game with the players.
NB: I'd been playing CT since '77 before that, so I knew how to run that, and my working plan was to fall back to it whenever I ran into something in MGT I wasn't sure of myself on.