Where do you get the tools, and how much would you expect to pay?

I don't know what the Omega back is like -- it might require some special,
hard-to-obtain tool -- so I can't give a definitive answer.

The most-common backs use either a slotted ring -- which can often be
removed with a pair of chain-nose pliars -- or a press-to-fit back, which is
removed with a "case-back knife".

The latter is simply a knife with a very thin blade. You simply press the
knife into the seam, and twist a bit. (Well, that's the theory. It's
sometimes a bit more difficult, and there is the chance of scracthing the
back.)

These are available from Zantech (http://www.zantechinc.com/store). They
have all kinds of watch-repair equipment and supplies. You'll have fun
browsing the site.


I don't want to be a jeweler, but $35, when I know the battery
could be purchased $35/100 from China, seems a little rich.

You can get batteries even cheaper than that from Zantech and similar
companies.

Any jeweler who charges more than $5 for a battery replacement -- including
the battery -- is gouging. Most batteries cost the dealer less than 25
cents, and replacing one takes less than five minutes. That's a gross profit
of more than $50 an hour. Not bad.