Automatic Transmission - Stock Tranny Program

I was beating on my Trans Am a few nights ago and noticed that it was redlining in 2nd gear, and not shifting into 3rd.

Does the 4l60E shift into 3rd at WOT? Where should my shifter be in (3rd or D?)

Shift Kit worth it in stock tune car? Is it something I can do now, and have a tuner help me out later, for the most benefits.

Thanks in advance.

It should shift into 3rd at WOT. It will not, however, shift into OD at WOT on the stock tune. Does it shift if you back off the throttle when it's trying to grab 3rd at WOT? I suspect the 3-4 clutches have burned up.