After system didaster how to prepare / save most important data ?

[SYNass IT Ubuntu / Linux]

Hello Ubuntian's
Looking & searching for a "Mounting local file" failure ...
... I ran into a disaster yesterday. ;-(

GParted (with Ubuntu 7.10 plus from RescueCD and V 0.3.6) shows nothing
anymore. ;-((

Fortunately I got MBR restored ...
... and can access both OS's (WinXPP and Ubuntu 7.10) again. ;-))

Now I prepare for extracting the most important data and appreciate 
your hints und suggestions to get this done best and safest to 
do a new system setup from scratch !!!

My plans and intentions:
1st: Save /home completely to a USB stick or external USB HDD !
2nd: additionally Backup Evolution to a separate USB stick !!
3rd - Thunderbird offers an import feature: How do I get Thunderbird's
data exported ???
4th: any further hints and suggestions are very appreciated !!??

After having all important data extracted ...
... how can I verify to have good backups / saves ??

As a Linux / Ubuntu greenhorn I appreciate simple and secure
suggestions 
possibly with samples how to do and eliminate insecure feelings ! ;-)


Recently her in the forum was a discussion about problems with hda / sda
while upgrading from Ubuntu 7.10 to 8.04 ! How comes and how to
overcome ??


Would it be better to reinstall 7.10 and wait some more weeks before
installing 8.04 LTS !?
I do not want to have problems with Foxmarks on this installation too !!


TIA for your help.
Cheers, svobi