Just an update since starting this thread; Per dealer incouragement, I continued to drive as the grinding became progressively worse, keep in mind I was taking my frustration out on it as well..
Finally refused to engage second a week ago, 5k miles. GM originally reccomended repair, 2nd gear, synchros, main shaft, and various other parts. When parts were unavailable, they sent replacement tranny. Just got it back yesterday, taking it easy on it for awhile, but so far so good.
