IIRC they are mounted to brackets bolted to the chassis, the easiest way will be to do one at a time, removing the brackets.
Youmight get away with removing one bracket and doing the other side by lifting the gearbox on a jack, there is more room to one side than the other.
You should also change the engine mounts, I chnage mine by lifting the nose of the engine and shoving it sideways, but it's a just-and-only. Once I had to remove the engine mount bracket too.