Huzefa,
as far as mats go, you should be able to find closed cell foam mats pretty cheap. In Aus you can sometimes get them for only about US$2.50.
Making a quilt should be pretty straight forward, especially if you use a synthetic fill like Climashield Combat…there is another forum thread going on at the moment where they are talking about this.
If you are carrying minimal other gear, in terms of shelter, etc, then having a sythetic quilt makes alot more sense than down, as you don't have to worry about it getting wet so much.
I'm sure you will enjoy Khardung La, even if it isn't quite the highest. I've seen some magnificent pictures of that and other passes taken by cycle tourers.
Have fun!
Adam
Edit: I am seriously considering giving this a go myself…