Ok, for my first mod using the get. I dunno if you could really call it a mod, but here's what I did.
I opened the geck and loaded the anchorage esm because I wanted to modify the gauss rifle's clip size and ap's.
When I saved the modified esm I named it anchorage1.esm.
since it is the identical esm to anchorage.esm except for the modified gauss rifle, will I need to select the original anchorage dlc at the data screen if I want to play the operation anchorage add on or will my new anchorage1.esm work the same?
also when I select which add-ons to load at the data screen, can I select them all and then play them as I get to them in the game? that's what I have been doing but i havent embarked on any of the dlc add ons yet.
any helpful advice would be much appreciated.
Thanks again, erich

You can't modify/save master files (esm's) in geck. Thats why it prompts you to make a new save when you make changes to them and you can only save them as plugin (esp). Just because you named your plugin esm it won't turn it into a master file, it's still a plugin but with a wrong extension which will prevent it from being activated next time you'll try to load it into geck to make more changes (yeah, it looks at the file extension rather than checking if it's actually flagged as esm, stupid geck). This plugin will only contain changes that you made (compare the sizes of your anchorage1.esm and anchorage.esm) and is basically used to override those specific stats in the master, or add a new content (such as your new armor).

Any master files that were loaded when you saved your plugin will automatically become it's masters (even if you haven't really used their assets) and will be loaded with your plugin when you launch the game regardless of whether you've activated them in the launhcer (or crash your game if you deleted them while your plugin still requires them).