2. The process will wipe all your apps. This was actually a bonus for me as it allowed me to start afresh and only re-download the ones I needed. If you do have any precious apps you can't replace or if you don't want to spend time re-installing I believe you can use a programme called "Titanium Backup" to save and restore apps.
3. If you have any personal data on the phone (photos, documents, calendar, address book etc) then you may want to back it up before you proceed. I didn't bother because I have long since moved any important data to cloud storage using Gmail, Dropbox etc. Phones get lost so you really shouldn't rely on a phone to store anything important. I notice that the upgrade seemed to delete save games for some installed games but not for others so probably best to assume that it will delete everything.
4. You should be aware that Cyanogen does not support the built in FM radio. I believe there may be an app available for this but I don't use the radio so I didn't bother looking into it.
5. The other big thing that is missing is the Samsung Store. I doubt Samsung will let you install their store on an unofficial operating system so if you have bought any important apps from Samsung you may want to reconsider the upgrade (or perhaps use Titanium Backup to carry the apps over).
6. Cyanogen does not come with the Google Play store installed so the first thing you will probably want to do is get the correct version of Google apps (gapps) for your phone. You can download it from goo.im/gapps.This Youtube Video is a little out of date but it gives a pretty good idea of how to install the download. Once you have Google Play store up and running you can sign into your Google account and download anything else you want from the market.