[Tfug] debian quandary: install 3rd-party deb, upgrade to etch or sid, or compile upstream?

[t takahashi]

i run sarge, with a few packages that are from a previous etch or a
previous sid.  no problems for years until now.

there are just a few packages that i need new versions for.  i can no
longer pull them from etch or sid because they would pull in something
fundamental, like a new version of libc.

i tried apt-get source then apt-get build-dep, but it says "no
available versions of package xxx-dev can satisfy version
requirements".

upstream for one of the packages has a deb for sarge.  if i put that
site in sources.list and install the package, will it destroy my
existing version?  will there be a way to go back if i uninstall it? 
will there be a way to go forward to sid if i decide to upgrade to
that?

is there an easy way to somehow statically compile from upstream and
make a package that can be uninstalled to go back to what i have now
if necessary?

i looked at debootstrap and pbuilder, but they seem a bit complicated.
 i am unclear on how or when to use them.

i am tempted to just bite the bullet and upgrade or dist-upgrade to
sid and be done with it, but since it is only a few packages i thought
i'd ask first.  that seems to be a one-way operation.

thanks.

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