Will I lose anything when I update my iPad2 from ios 4.3.5 to ios 6

Hi, I have just backed up my iPad 2 to my computer and was about to update it but then it said "Updating to ios 6.0.1 will delete all the apps and media, including i Tunes Store purchases, on your iPad . To preserve your content , apply this update on the computer where you sync apps,music, videos and photos. Updating on this computer will only preserve contacts,calanders,text messages and other settings ..."
So am I right in thinking that when the update is finished the iPad 2 will be like it was when I bought it or will it be the same as before ?

Additional Information:
Also I did used to sync it with another laptop but I dont use that one anymore, but I do still have it
When the update is done will I still have my in-app purchases like episdoes of The Walking Dead Game or will the app just be as it first was
I havent jail-broken or hacked by device in any way