I bought a new stock and a telescoping stock wrench and I don't know how to remove the old stock. It has the fixed position telestock on it now. I found instructions on how to put the new one on but not on how to remove the stock. Any help or instructions would be greatly appreciated.

Thanks

Reverse the install directions. j/k.loosen the castle nut with the wrench all the way to the end of the threads. It may be staked. pull back the locking plate, but go slow cause there is a spring and detent pin on the right side for the rear takedown pin. unscrew the buffer tube from the receiver and make sure you hold down the buffer retaining pin andslowly relieve the pressure once the buffer tube clears it. install new stock

How might one unstake the receiver extension nut?

You can't unstake the castle nut.  Using a CAR wrench might not work either.  I broke 2 CAR wrenches ( one at the tooth, and the other bent in the middle. DPMS) trying to loosen that damn castle nut from the factory buffer tube.   I even tried a vice grip and pliers to no avail.  If the new stock comes with new hardware then your best bet is to use a dremel and "splice" the castle nut off making two slices from one notch to the stake.  Prefferably at 9 and 3 o' clock, then carefully pry the nut free.  It doesn't matter if you scratch the post ban buffer tube or the locking plate cause hopefully you have new ones.  Just be very careful not to scratch the receiver.  Take your time, I dremeled mine off in about 10 min.  I can post pics if you want.

I believe it is staked in place.  There are little notches in the back side of the castle nut with what looks like pins protruding through them.

Yes it is staked (damn you colt).  There are no pins holding the nut and plate together, they are just "punched" so the metal from the plate is binding into the groove on the receiver end of the castle nut.  This is the reason you cannot unscrew the castle nut.  I'll try my best to show you what to do but I cannot find the old castle nut from the post ban buffer assm.  Try this anyway.  get out your dremel with the abrasive cutting wheel (not the sanding disk).  go slowly unless you trust your steady hands as to not scratch your receiver.

[ img]http://tinypic.com/eec6v

The above picture:  imagine the castle nut on the left of the plate... you can see where the dremel was used to cut from the notch on the left of the nut all the way THROUGH till the staked part of the plate.  I did this on two sides so as to splice the nut off.  one cut at about 9 o'clock and the other at about 3 o'clock, both cuts from one end of the castle nut to the staked part on the plate.  Once you do that you can physically use a flat head screwdriver and pry the two pieces of the castle nut apart ( enough to remove it).

[ img]http://tinypic.com/eec78

In this picture:  this is the new hardware as I don't have the old anymore.  The splice you want to make is literally from the notch on the left of the castle nut straight (actually diagonally) to the notch on the right of the nut (this is where a stake on the factory plate would have been).  and do the same for the other side.

Try this and let us know how it goes.  I'm sure you don't care about the fixed buffer tube now that you have a tele stock so you shouldn't worry about scratching that up. You want to dremel ALL THE WAY from one end to the other,  But when you start getting close to the receiver, just go slow, take a break if you need to, little by little.  Pry with the flat head screwdriver by sticking it in the cut and twisting the handle clockwise/counter.  If the nut doesn't separate then dremel a little more.  good luck.  Sorry I didn't have detailed pics.

It's been a long time since I had to remove a staked on castle nut , but the last time I did I just used a 1/8 inch drill bit and drilled just enough to remove the staked part.
As I recall it worked very well.

You may try to heat it up a little just in case it has locktite on it.

Court 223  (aka Court in FL.)

Yeah you could do that also.  It does have a little loctite on the nut but if you have channel pliers you can break it free.  Let us know how it goes.

Thanks for all the ideas guys. I'll have to pull some tools out when I get back from our FTX this weekend and see what I can do.