Well it is possible but I am a bit scared of distros like ubuntu which do not set a password for root by default. They can still be fixed, but it is more work.
change the owner UID of the gutsy /home/ryth
Possible, but you have to be root somehow. Booting from a live CD and mounting the home partition is also fine. Now
If you are working from a live CD, you will have to replace /home/ryth by "path/to/where/home/partition/is/mounted"/ryth.
sudo chown -R 1000:1000 /home/ryth
Not only this, once you are root in live CD, you can also change the UID of the user ryth. Edit the /etc/passwd file (path will be different if doing this from live CD). The third and fourth fields are UID and GID. Change them to your lucky numbers, change ownerships if all the files you need and celebrate. But ensure uniqueness and validity of UIDs and GIDs in /etc/passwd. Hell hath no fury as /etc/passwd scorned.
Hardy install it shouldn't overwrite anything in the current /home
As far as I am aware, OS installation never changes anything in /home. When you try to login, initialization scripts will be picked up from your home directory. If you have permissions to run them, fine. Otherwise login completes with errors / fails. When you start an application (say firefox) it looks for its initialization folder (~/.mozilla/firefox). If you have appropriate permissions on them, fine.