Originally Posted by vici0us
is it possible to upgrade to v21 from v18 w/o having to wipe all my datas and contacts?
You can try to update without doing a full-wipe (not recommended though). If you get a boot-loop or some other weird problems you know what to do (Reboot into CWM and Full-Wipe).
As for contacts ...
If your phone is linked to a Google Account your contacts are actually backed-up on that account. Once you set-up the account anew (on a full-wiped device) the contacts should be automatically be imported.
SMS can be backed up, and restored, through "SMS Backup+" (search for it on the Market) ... the app is using your Google Account for that matter as well.
Data/Apps can be saved and backed up through Titanium Backup, though I never used that way.