Chunkie

There is a huge difference between a match guide which sit very high off the blank and the micro guides that are being used on bass rods. The micro guides are really fly guides in a size 3, 3.5, or 4 and are tight to the blank.

Changing the rear grip should not void the warrenty but you could check with St croix first. If you are going to this and want to use preformed cork then you will require 2 2 1/2" fore grips and a rubber ring for the butt cap and 2 winding checks along with some rod bond or an water proof epoxy.

I would say just slightly butt heavy. so the tip of teh rod wants to come up.

3 cc is a good number of each part; you will have left overs on you flat sheet of tin foil

Yes you can repair it and quite easily too. http://www.rodbuilding.org/library/repair-oquinn.html check this out. The rod will be as good as new and no you will not change the action.