I have an 02 dmax with 272,000 miles on it and the motor shakes at idle (bad) and at 1200 rpms it gets worse (very bad) and at 55 or 60 mph its not so bad (almost normal). Did I break something internally with the motor or....?

 

Perhaps the injectors are out of balance? I'd check the balance rates and make sure that they're all functioning properly.