File Processing help wanted

[David Chart]

I'm about to move my entire website to a new domain and host. Moving to 
the host is no problem. Moving the domain means that I want to put 
redirection signs in the old account.

However, the website is quite big, so I really want to automate part of 
it. I'm sure this should be trivial to do under Linux, but I don't know 
how. Instructions or pointers to instructions very gratefully received.

First, I want to replace the contents of every .html file in a hierarchy 
with a single file. (This file will just contain a link to my new 
website.) I want to keep all the names intact, so that bookmarks to the 
depths of the hierarchy will still get the redirect. I'll be doing this 
to an exported copy of a CVS module, so nothing will be permanently nuked.

Second, I want to replace all strings of the form '@dchart.demon.co.uk' 
by '@$mynewdomain.com', in the same hierarchy.

I have a strong belief that both of these tasks should be trivial...

Thanks in advance,
David Chart
(Note: I *can* read replies to the list. The massive number of viruses 
coming to this address is one reason I'm moving.)
-- 
David Chart
http://www.dchart.demon.co.uk/
Email to this address is deleted without being downloaded. Replace my OS 
with my first name to reach me off-list.