iPhone 3GS sync question

I just got a new macbook pro and now that I'm trying to get things from it onto my iPhone 3GS it's saying it can only be synced to one iTunes Library at a time.. So it gives me the option to Erase and Sync.. If I do this will I lose all my contacts and photos as well? as far as music and ringtones I'm not worried cause I have all that backed up.. but I don't want to lose my photos or contacts.. Any help would be appreciated.. Thanks

Not sure where your old iTunes library is located but if you transfer it to your new Mac your phone will just see it as the same library and you won't have any issues.

If you want to start afresh:
- You can use Image Capture on your mac to copy the photos from your phone.
- You can use an iPhone app called iDrive (free online storage and app that allows you to backup you iphone contacts)

Once backed up you can erase and sync then copy back the photos with iTunes and re-install the iDrive app and restore your contacts.

As an aside if you setup a gmail account you can wirelessly backup and sync your contacts without even thinking about it. Set Up Your Apple Device for Google Sync : Google Sync - Google Mobile Help

Let us know how you get on

If you head into the sync options for contacts within iTunes, you will be able to merge all the contacts from the iPhone and your Mac without losing them in either location.

Having the backup of them as mrplow suggests is not a bad idea though.