firmware upgrading question

Right, i'm starting to finally get all the probs that i see posted on this forum, the reboot crap, the ghost txt messages that you receive but are never in the inbox, low battery life and now messages i'm trying to look at that i received ages ago don't come on the screen when i click on them, instead i get sent to a totally different one.. ???
Also when i try to cycle through them to get to the one i want then i seem to get message has caused an error and will close now, then it goes straight back to the usual wallpaper screen with your basic options on it.. wtf?
anybody got any ideas why?
and if i get to upgrade the firmware what will i lose from it, will i lose all my txt messages because there are a lot i need to show to someone soon but can't afford to lose them.
any help would be helpful indeed..