If they look cracked at all, they should be replaced. I think it's too hard to move the engine & trans by hand to check for failed mounts, so trying to do so won't yield any useful information on their condition. But anyway, if you have cracked trans mounts, and are experiencing shifting issues, you might as well just go ahead and replace the trans mounts. They're cheap and easy enough to replace, and it sounds like you need them anyway, so it couldn't hurt to give them a try.
1998 BMW 328is
1966 Pontiac GTO
2007 Subaru Impreza 2.5i 5-door
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