Ok, it's pretty simple when all you're doing is changing buttons that are already there....For adding DVD2XBOX, find the part in the custom1112_GamesHome.xml that says "Emulator Push Button" or something like that, and change the onclick part to say <onclick>XBMC.RunXBE(E:\Apps\DVD2XBOX\default.xbe)</onclick> (or whatever the path to DVD2xbox would be in your case). Then, where it says <include>1002398</include> (i just made that number up, but it should look something like that, in the same little group of lines as the onclick) change it to say <label>DVD2Xbox</label> or wahtever you want the button to say on it. Then, if you want to change the description on the right to match, find the part that says something like "emulators multiline description" or something, and where it has the include that looks similar to the one i posted above, change that so that the ends say label instead of include, and in the middle, type what you want it to say....Make sure when you're replacing these includes, you don't replace the wrong ones. There will be others mixed in there too, but those should have words instead of numbers
Then, for linksboks, basically do the same thing, only looking for the Game Saves button instead of the emulator button to modify....Or, instead, you could add an entirely new button, because it's already set up to do that. if you look toward middle/bottom of the xml, there will be a part talking about "custom push button" and stuff. Just add in your stuff, and delete the line that says <visible>no</visible>, or if you only want that button to appear when you have an internet connection, you could make it say <visible>System.HasNetwork</visible>
Let me know if you need more clarification...