Is there a DirectX or VST app that will replace track parts such as a recorded kick drum with sampled kicks? I'd rather not do it with copy and paste. I know ProTools has this feature.

Drumagog, Trigger

Never tried it but it seems that I remember reading somewhere that it can be done with V-Vocal. Not sure though.
 

The SONAR way would be to use Audiosnap. There is a video about it here http://www.cakewalk.com/C..V/SONARU.aspx/Go-Deeper AudioSnap 2.0 Drum Replacement

There are a couple of threads in the last few months about using Audiosnap for drum replacement here is one of them http://forum.cakewalk.com/fb.ashx?m=2655971

yes Audio snap, do it all the time, it's a ,,snap? 
It only works on  a monophonic- transient type audio tracks like a kick or snare. You tell it what MIDI note value and it creates a MIDI track.       and then you can assign that to any soft synth, sample player like say session drummer.      

Awesome! Thanks for the help!