Ok..so I went to the store and bought a bag of MiracleGro to get this initial stuff taken care of. I moved some of my vegetables around and followed the above advice. We'll see what happens! Of course I waited to do all my replanting until the hottest day of the year, so hopefully the heat won't kill them!
I'm such an amateur.
Going forward I'm definitely going to look into the DIY stuff. That all sounds great, and pretty simple! I think it would be a fun project to take up a little time in the winter too.
Thanks everyone for all of the great advice!! I'll let you know what happens!