Ah, another bidding modeller! If you're interested in modelling, I strongly recommend blender. It takes a while to get used to, but is worth it in the end. Yes, your first idea looks pretty easy, one could probably do it in less than a minute. But if you are completely new to modelling (an assumption) it's probably better you learn about making stuff from scratch, rather than editing.
Just follow
Blender 3D : Noob to Pro, and just muck around with blender. While weapons are relatively easy to model, they have a few restrictions in that they need to fit the existing hands and animations, as well as not going too far beyond the hitbox.
I'm learning blender by just making a few simple props, not even finishing most of them. You'll spend a good deal of your time learning about what tools you have available, and as any artist will tell you it takes some time to get proportions right, as well as looking as you want it to. Also,
http://forums.tf2maps.net/showthread.php?t=12592 is indispensable.
Finally, make sure to always have HEAPS of reference pictures of what you're modelling, and always take Selentic's advice with a pinch of salt.
Good luck!