So I'm trying to make a map, but I have encountered more problems in about two changes to a unit than I ever have before. First, I want to change the cost of a photon cannon, but I have no clue how. I changed some properties of the cannon, but then its attack disappeared. Also, how do I change the name of units? I tried to change the name of an archon, but I don't understand it at all. Lastly, this isn't related to the data editor, but how do I place map revealers?

Use the search function.
http://www.staredit.net/topic/11181/

I used that, and I tried to search for the cannon, but I couldn't find it under anything in the abilities tab.

I believe I did an awesome job in recreating devilesk's picture.

Yes, you did.
With this System it's possible to build the same building with different costs/time/... . That's why they made it like this I guess.