That is a good price...let them do it.
Problem w/ freeze damage on 825y is that some of the EXTERNAL parts could be cracked/warped and you won't know until you install the kit. If you want to tackle it, go ahead and buy the kit but make sure they will take it back....
Of course it will always be cheaper to repair something yourself..then have it replaced or repaired by others..but what is your time worth?
Why isn't the company offering to repair rather than replace? Ask them....they will probably tell you the same thing I have mentioned.
Good Luck
Sprinkler Solutions, Inc.
Arizona and Colorado
www.sprinklersolutions.net