I've done it on several occasions, and have had no problems. The real key to this is the piece you use to splice the the two tubes together...the one from the original gauge, and the one from the donor gauge. The donor gauge you will use will most likely have a slightly smaller diameter then the tube coming from your original gauge. You have to get both ends to fit faily well, which will mean drilling with different size drill bits. The solder joint MUST be good, or the ether will leak out and then it's start over with another donor. Carefully inspect the solder joint BEFORE you take the bulb out of the salt/ice slurry. Other then that, follow the instructions and it will work.
I repaired the one on my TR3 a couple of years ago, and it's still working fine.
BTW, the slurry of ice water and salt dropped the temp down to below 0 deg F. Plenty cold enough to keep the ether in the bulb.