Change models, help or a tutorial needed

Hello forum, I'm new with the Quake Engine, but I have experience under Ubuntu, Windows 7 with Blender, 3ds Max, Cryengine 3 and Unity3d. I'm really impressed with that, what the developers of Xonotic have done with an modified version of the Quake 3 Engine I've decided to add new models for testing the engine a bit, but I really don't now where to beginn I have some weapon models (not createt by me) and I want them to convert into .md3 or (iqm,iqe). I prefer to use Blender but I don't now how to configure or install the Inter Quake Exporter and how all this works.

Can someone help me, I haven't experience with modifying (editing) Xonotic

actually its quake 1 engine hehe

Uh no, it's DarkPlaces.

Ok, Quake 1 Engine ^^
I found this site in the wiki with some models (.blend iqm.framegroups) http://dev.xonotic.org/projects/xonotic/files
If I create a model like that one in the .blend file, I just have to export it in .iqm.framegroups and then I can replace the orginal model in the Xonotic folder, right?

Actually the .framegroups file is not a model, it is a file that tells the engine about the animations from the actual model (the .iqm file). Some information about this here: http://dev.xonotic.org/projects/xonotic/...ramegroups

I have no experience with weapon models, so unfortunately I can't help with that. But for player models you can have a look here: http://dev.xonotic.org/projects/xonotic/...der_to_IQM

Exporting to IQM is very straightforward, basically you select the objects you want to export and the armature, then in the IQM exporter dialog you specify location and a list of animations separated by comas. It should work right away in the game, however if you have animations you will have to create a .framegroups file so engine knows about them. I have no clue however if it is the same for weapon models, hopefully somebody else can help.