Hello!
To begin, I strongly recommend that you successfully complete the entire series of Bethesda's G.E.C.K. introduction tutorials -- http://geck.gamesas.com/index.php/Category:Getting_Started#My_First_Vault_Tutorial_Series -- if you have not already, as it is very beneficial, easy, and fairly quick.
In regard to you first question, the G.E.C.K. generally operates by plug-in's, which basically load from a master file (Fallout 3, in your case) and any changes are saved in this plug-in file, thus when using this mod its only a very small size (only the changes are saved to it). So, I would suggest starting over again: first, load the Fallout3.esm by double-clicking it and selecting OK; once loaded, save (ex. press the save icon/button) -- this prompts the creation of a new plug-in file (.esp), so, put in your desired name; now that you have a plug-in, make the changes you want to the form ID (here, the 32. pistol), and save! Now, to have these changes -- or plug-in -- applied, when the Fallout 3 launcher comes up, go to Data. Your new mod/plug-in should show up here. Double-click it, select Okay, and then Play! Also, as a note, if you want to make a change to the 32. pistol you see and find in Fallout 3, that is, the original weapon, or any other object (form ID), so it is applied to each and everyone of them, simply go to it in the G.E.C.K. (here, Weap32CaliberPistol), and directly make the changes -- there are other, well known ways to do this, of course, such as through FOMM. However, if you only wanted to have a certain number of the 32. pistol's changed, or you wanted to give it a different name while keeping the original 32. pistols, also simply go to the ID field and change it to what you want (this is the form ID or editor ID that appears in the G.E.C.K., not in-game), and after applying your changes or whatever and saving, it will ask you if you want to create a new form, which you do, and there you go -- you have a new form ID, thus, the original 32. pistol remains unchanged and you have a new one (which of course exists no where in-game as you have done nothing with it yet)!
As for your second question, I do not quite understand.
Similarly, for your last question, I also am having trouble understanding.
Thanks for the quick reply!
1) Right... I think I understand, so I open the Fallout 3 master file, and save it to the Fallout 3 data folder (naming it whatever, e.g. 32. pistol fix), I then go to said data file, double click, and press "ok" and then... it loads the game with the changes?
See, I use FOMM as my launcher, so I don't know whether that would work or not, unless I basically copied the Fallout 3 master, made changes I wanted, then deleted the old one, so the only one FOMM could load would be my modified one... is this correct?
2) In response to your comment that my second question was difficult to understand, I'll try to phrase it differently
When I go on the GECK, and click "open file" I'm presented with a list of all the master files and...plugins is it? (the mods?) that I have installed. Now, I have a mod which is a master file, which also relies on the other master files I have installed (Fallout 3, Anchorage, Zeta, Pitt & Maryland (don't know what it's called of the top of my head, the one with the evil brain)
Now, when I try to open the master file which relies on these other masters (the GOTY add-ons + Fallout 3 itself) it simply aborts the load saying that more than 1 master file cannot be loaded at the same time. My issue is that because it does this, I cannot make any modifications to my master file mods which rely on the GOTY add-ons + Fallout 3. Is there a way I can open them without having to open Fallout 3 +GOTY add-ons? Because when I try to do so (set as active file etc), it automatically trys to open all the other ones
Is that clearer?
3) Last question regarding ID numbers. You know how all items in fallout are assigned an ID number, which via console commands, we can use to obtain the item "player.additem XXxxxxxxx 1" All I want to know is if this number is found in the item files is in the GECK, and if so, where? and if not, where can I find this information
Thanks