iPhone question

I bought an iPhone awhile ago and the person that sold it to me said NOT to upgrade it to the latest version because it would "lock" it. When I open my iPhone it says dejavu version 1.4 if that helps. I would want to upgrade it to get the latest apps and stuff.
What do I do to upgrade it? I can't do it from iTunes when they prompt me right...????

step by step instructions --> http://www.iclarified.com/entry/index.php?enid=1880

Castro said:

It's a 2G ? You need to use quickpwn. http://www.quickpwn.com/

Click to expand...

it's not the 3G, so I guess it's the 2G.
Gadha, I checked the webpage you just sent me, thanks, it will still work if I have a very old version (probably 1.4 if that even exists?)
Will I lose all my data (contacts,texts,pictures,etc.) when upgrading?