Just FYI - final info just in case anyone else ends up needing to replace sockets:
I used the following socket purchased from Autozone - Durlast 383 socket
http://www.autozone.com/1/products/65435-socket-383-duralast-383.html
It is different from the original in that it has 3 wires, one of them being a dedicated ground wire. The original sockets have only two wires and the socket is grounded when the it is attached to the metal bucket (which is itself then grounded). The new 3-wire sockets ground both through attachment to the bucket and the dedicated ground strap.
The sockets insert from the back of the bucket. I glued the new sockets in with "Marine Goop" on the back. Let it dry for a day+. Seems to work very well.
I did not have to replace the flasher unit. The one that's already installed seems to work fine (whether it's the original flasher unit or not - I don't know).
These "Plasma"/LED tail lights are very bright