Running 3.5.1. Is there an easy way to display my most recent post in its entirety and only display excerpts for my older posts on my home page?
This is the basic idea behind what you want. Extend/Customize to your liking.
Or if you want to ommit the compare and the increment operations:
// EDIT to get the one-and-only most recent post in full only:
|show 4 more comments|