1 - will i be able to download all of my apps for free again.
Yes. It should also be saved in your iTunes library so you can simply sync the iPhone 4, and you will have everything that your 3GS did. If you are missing an application, login to the same iTunes account that you used to purchase the application, and Buy the application again. During the purchase process, it will tell you that you already purchased it and will prompt you to download it for free.
2 - will i be able to copy all of the contacts across easily
You can sync contacts and many other things into iTunes when you sync your 3GS. It will also backup precious data such as game saves, or application preferences. You can simply then go and setup your iPhone 4 as a backup of your 3GS and gain everything that the 3GS had.
3 - i do not have iTunes managing my music... i simply create playlists for every album, copy them to the phone and then delete the album from my desktop so i am not worried about the music but i presume i need to delete the 3GS profile on iTunes and set up a new profile for the 4G
By profile, do you mean current setup on iTunes? You can simply sync your iPhone 4 and you will have everything exactly like your 3GS, provided you have setup your iPhone 4 as a backup from the 3GS. It will prompt you to do this when you first connect your iPhone 4 to your computer. Prior to getting the iPhone 4, sync your 3GS with iTunes once. This will allow it to fully backup and have your newest data saved before you start working with your iPhone 4.
If you have any other questions, feel free to ask.
