The Brawl moveswap list has an extra line of placeholders in the 'code content' of the ocarina code manager. What do I switch out the placeholders with?

Tell me if I'm wrong, but by place holders you are talking about the "XXXXXXXX XXXXXXXX", correct?
If so, look at the "Code comment (leave empty for a category)" box directly below it. If you scroll down a bit you will see a list of codes followed by character names.
Just replace the "XXXXXXXX XXXXXXXX" with the the move set of choice.

So if you want to replace Ganondorf's moveset with that of Pikachu's, just select Ganondorf under "Moveswaps" and replace the "XXXXXXXX XXXXXXXX" with "34832B63 0039E8E0", then select "Store modifications".

I'm taking this information from the "Wii Cheat Code Manager" in which I think you're referencing.

Hope I helped,
- CheeseKeg.