If you have pictures, just use imgur and link them here.

Everything you asked was explained in my tutorial videos: http://steamcommunity.com/sharedfiles/filedetails/?id=113161455#

If that guide still doesn't make sense, then watch my very basic TF2 one here: http://www.youtube.com/watch?v=-X5QGx2TP_8

Testing your model in-game is just a matter of compiling your model using the in-game compiler. It lets you preview it in-game as well as test your item out in a bot game. I explain how to rig models in the video (watch it) as well as how to export models as smd files.

Valve put together a bunch of very detailed PDF files that explain exactly what each mask does. They can be found at the top of the technical requirements page here: http://www.dota2.com/workshop/requirements

You are better off using Photoshop for texturing, btw... but if you can't get a copy, then I'd say use GIMP because I don't have any experience with Paint.net.

Your last question involving unwrapping: You can unwrap things however you like. You can use a combination of seam unwrapping and projection unwrapping. The important part is that you don't need to unwrap the whole model at once. As long as you can unwrap it in a logical and easy to texture fashion, you should be good. Also... make sure that your seams aren't in visible places (try to hide them inside other geometry or on the backside of the model).

You'll need to use facial flexes for that. Warning: facial flexes are NOT easy. Napy de Wise made a tutorial on how to do that here: http://steamcommunity.com/sharedfiles/filedetails/?id=170877216

Manipulating the alpha channel itself is hard since you don't have things like layers to work with. I suggest making the alpha channel in a separate .psd document (and then when you are done flatten the image and copy/paste it into your actual mask files).

If you notice, none of those weapons are gold-starred. And if they are, then 1) it's breaking Valve's rules and 2) they don't have necessary things like physics models that you normally need when making weapons. I wouldn't waste my time making weapons if I were you; as much as I love making them myself (most of my submissions pre-beta-import were weapons), Valve seems to not want them.

Very cool! Maybe this will be shipped during Halloween! Good luck.

You can't import weapons. Valve doesn't want weapons, so don't submit them. Basically it takes so much more time to come up with a new gameplay mechanic (that is balanced) and code it than it does to just ship a new hat/misc into the game.

Valve might add weapon support for the new importer in the future, but it's highly unlikely.

It's really just a matter of experimenting. The thing that might help you is importing animations so you can see how the bone weights will look while a character is running/shooting/etc.

There aren't really any tf2-specific tutorials I can link to. I would just google a few rigging tutorials and see what is best.

Are you looking to do facial flexes? Look up Napy De Wise's tutorial on facial flexes: http://steamcommunity.com/sharedfiles/filedetails/?id=170877216

Oh... if it was just a blender thing, then it was probably that you had insufficient lighting in your scene. You can solve that by either adding more lights or simply deleting all of your lights (and the scene will become fullbright).