By fenders I am not talking crappy mud flap plastic fenders. I am talking real wrap around full coverage fenders like you would find on a commuter bike. I have a Trek 4300 26in mountain bike. Two bike shops said it is not possible, but alas, the internet says it is! One shop got some 700cc fenders, and they ALMOST fit. I would just need to replace my studded tires with thin commuter tires. The V breaks got in the way a little, but I think there was some wiggle room, or I could get disc breaks. Plus the frame has mount points for fenders, so there must be something out there.

So my question, has anyone put real fenders on a mountain bike?

I've put fenders on mountain bikes before. Quite simply, metal doesn't scare me to bend, cut, and weld.

But how far can I get if I have really no metal working tools?

When I work on bikes, I use the most basic tools I have. I mean, I have quite a few metalworking tools, but I prefer to use a hack saw to anything else, and I typically avoid welding on a bike because I'd rather make something out of one piece than weld it together.

With a hammer or two and something the same basic shape as a fender, and you can bend one to fit. Most of the time, you don't need tools, just bend it in your hands. Fenders are incredibly thin and easy to work with.

its definitely doable if your willing to a little customizing. i don't see why you couldn't just carefully bend some fenders out with your hands/fingers enough to make room for knobby tires and then cut some notches to clear the brakes. if notching the sides would weaken them too much you could reinforce them from the inside with bits of scrap metal and rivets. just remember when your bending metal its best to work slowly and take baby steps, trying to bend metal too fast or all at once causes creases. I don't know how the front fender mounting bracket would work. I'm assuming you have a suspension fork in which case you would probably want to mount it under the arch. you may have to ditch the bracket supplied with the fender and use some adel clamps to attach it to the fork arch otherwise you'd probably have to drill and tap a hole in the arch

Yeah I was thinking adel clamps or something of the sort would have to be used to mount to the front fork

Planet Bike fenders:
http://ecom1.planetbike.com/fenders.html

I think those were the ones that didn't quite fit. Or something similar.