Hello Salama,
I also did an upgrade last night, and I also had never done one previously. My steps were
1) type into Google "upgrade DotNetNuke"
2) I noticed the few hits for DNNCreative and then I noticed Mitch Sellers also mentions upgrades
3) clicked on his link,
4) read on first page and noticed that he has a special article on how to upgrade from 4.x to 5.x
5) Read second article in 2 minutes where is basically says back up first then extract over the existing installation.
6) I then read his guide about how to do a backup (zip the wwwroot/dnn folder and back up the db completely)
7) I then xcopy-ed the entire app folders to a test machine and restored the db and in another 15 minutes I had a working UAT environment.
8) I then extract the new 5.1.1 over my existing 5.0.0
****************** FINAL STEP ******************
9) You must then navigate to a URL that Mitch provides which is
http://www.mysite.com/install/install.aspx?mode=install
For me on my UAT that all seemed to work, all modules look OK, even my ultra Media and Ultra Video TP modules.
Here is the first link on Mitch Sellers site.
http://www.mitchelsellers.com/blogs/articletype/articleview/articleid/55/dotnetnuke-upgrade-tips-lessons-learned.aspx
Here is the second where is outlines how to upgrade
http://www.mitchelsellers.com/blogs/articletype/categoryview/categoryid/21/dnn-installupgrade.aspx
Here is where he describes going from 4.6 to 5.x
http://www.mitchelsellers.com/blogs/articletype/articleview/articleid/278/upgrade-to-dotnetnuke-500-from-462-or-later.aspx
Here is where he outlines how to backup properly
http://www.mitchelsellers.com/blogs/articletype/articleview/articleid/164/how-to-backup-a-dnn-installation.aspx
I hope that is useful to you, and I thank Mitchel Sellers for his efforts
Mark Breen
Ireland