You should be able to target the cart button with jquery and replace its “text”. The selector might change depending on the cart skin, I can’t remember offhand. Check this out. You may want to add something like:
to one of the shopping cart html areas.
As far as kicking off a campaign… I would recommend setting up some billing automation or product purchase goal. Unfortunately, there is not a way to merge “quote” specific fields into an email triggered from this.
If you want something that is this customized, I suggest looking at the api to accomplish each step, potentially with some customized flow on your end (not necessarily using the out of the box shopping cart).