I bought an old (guessing it was built around 1900 - 1920) mandolin the other day, and having cleaned it and everything, I've noticed that, because the wooden nut is so worn, the bottom course of strings will be producing more buzz than tone. The only solution seems to be to put in a new nut, which is fine, only I can't get the old one out. As I said, it's made of wood, and probably uses some weird old type of glue. Any tips?

P.S. I only paid £40 for it, so I'm not looking for a major job. I want to do it all myself... and I don't really mind about it being ugly or reducing the value of the instrument, I bought it so I could play it, not so I could look at it or resell it.
Maybe try heating the glue up a little bit? Then try using a small craft hammer, to knock it out.

Failing that, I suppose you could always use a junior hacksaw, to cut it out, because anything bigger would be too cumbersome to use accurately. After filing it down to the wood, it should be easy to get a new nut in.

I doubt thats helpful in the slightest, but in the situation, thats what I'd probably do.
Hard to say without pictures.
Dear God, do you actually answer prayers?

Yes, but only in a way indistinguishable from random luck or the result of your own efforts.
Unusual for a nut to be glued in. If it's that old, and there is glue, it's likely a "hide" glue which should loosen up with heat/steam.
Of course, you want to be very gentle so that your fretboard doesn't come loose at the same time.
You could, as stud muffin says, just remove it by force...very carefully. With the old material cleaned out of the nut slot, a new bone nut could be easily fitted.
Quote by Bikewer
Unusual for a nut to be glued in.

I don't think I've ever seen one not glued in.

Either way, a touch of heat and a firm but steady hand should do the trick.
I should have said, "with anything much more than a drop of glue".

With an instrument that old, it's almost certainly some sort of hide (animal based) glue and as you say, should yield to heat.
The guy who did the repair column in Guitar Player always recommended hide glue on parts you might want to take apart later...
Modern acrylic or cyanoacrylate (super glue) will be stronger than the wood...
lots of good advice, but if you are still unsure try asking on the forums at The Mandolin Cafe, those guy's get serious about all thing mando.
be of good cheer.