Switching from Etch to Lenny - help me assess the risk.

[Ramasubramanian Ramesh <rramesh@ti.com>]

All,

 I run Etch+backports at my home gateway/file server. Lately, I find 
that many packages are too old in Etch for my needs. I am thinking of 
switching to Lenny. While Lenny is not as stable as Etch, I am not sure 
how much difference there is, in terms of stability. I am not worried 
about a couple of packages breaking here and there  and X not firing up 
occasionally. I am only worried about complete breakdown like down time 
on this server. So here are my quesitons

Does Lenny breakdown occasionally completely? I mean you cannot boot 
after apt-get update.
Will it cause major data corruption due to its instability?
Will it have broken kernel?
Will my NAT and  firewall completely fail?
Will my samba+cifs+nfs service breakdown or cause data corruption?

Finally, if I decide to switch, do I do a apt-get dist-upgrade or just 
apt-get upgrade. What is the difference?

Regards
Ramesh