Some clarification... All information regarding gear ratios specific to this car was gained by searching this site yesterday. I rarely drive this car and have not been launching from stop lights. I'm a licensed road racer so it is not in my nature to go around launching cars from stop lights and I'm also adept at not destroying cars if they are designed and built properly. No one is driving the car incorrectly. The car is used mostly for city driving but it should be able to handle more than 90k with that usage. The car is also stock except for Blizzaks for winter tires and the successor to the RE730 used in the summer.
I want to do the 6MT because they have fewer reliability issues as far as I know and I would expect a fuel mileage increase due to lower revs. The fact that the problem can be identified w/o opening the case indicates that the current 5MT is not up to the task.
I will see my parents tonight hopefully they will have a document that states what the problem is.
Maybe the best solution is to get a junk yard tranny and try to rebuild this one so we can replace transmissions when the clutch is due.