Biggest hassle will be in getting the valve out of the line that it has been in forever. The fitting is barbed and the hose molds itself to the fitting and makes it a bear to get loose sometimes. If there is enough slack in the hose (usually is) then you can just cut the end of with the valve still in it or slit the end of the hose to make it easier to get out and then cut the slit part off of the end. Put a little slippery stuff on the inside of the hose and the rubber grommet and put it back together. As far as hot or cold goes, I have never taken the effort to make sure it was warmed up before I changed it but commons sense dictates that it will be softer and more pliable if it is warmer rather than colder.

Mark

Simple, pull it out, push it in. Sounds kind of bad.