Consquences of changing hostname

[Robert Ian Smit <robian@wanadoo.nl>]

I am used to leaving "Enter domainname" blank when I install Debian. 

So all my systems are called something like box1 or box2.

I want to add to this name so it becomes box1.foo.domain.

I have searched through /etc and i have found a couple of files that
reflect the hostname of the machine.

Can I update these files to the new name? I am most worried about the
exim and ssh(d) configuration? Exim for obvious reasons, and ssh for
fear of being locked out of remote systems (I use key pair
authentication and don't want to get on a bus to reset public keys.)

If I had entered a domain-name at setup time, would foo.domain just
be appended to the entry in /etc/hosts or would other configuration
have taken place? I compare to an OpenBSD box that is already setup
correctley wrt name+domain. That system uses an entry in /etc/hosts
and has the file /etc/myname. (It's apples and oranges, I know)

I want to be able to use short names as well. Is it possible to do
this with entries in /etc/hosts like:

192.168.1.4 box1.foo.domain box1

If so, would all regular network applications parse the entire entry
to find both names? (expressed from users point of view)

I could give it a shot, but I'd rather await tips and mentions from
this list. 

Bob