Make sure you are gauging your 'repaint' of the rear facia cost from the price it will cost now. You (I think) said you priced the front and rear before, but prices do go up. Also, a 'two-fer' (front and rear facia) usually costs less than a 'one-fer'.
The 'total' job vs the 'coating only' job makes sense. A warranty will make it a much better solution partially protecting you from a conflict with a prep vs paint problem.
.