To answer some of your other questions.
you have to look into the folder I pointed to above by right clickinig on it and selecting Show Package Contents. Then you are greeted with soomething like this.

In the Masters folder you should find a bunch of sub-sub folders that will hold all you images. you'll need to go through it and see what you want to copy over to the external or copy them all over to the external by last folder name which is more then likely the date the images where taken.
You may also be able to do it in iPhoto, don't know I really have never used iPhoto for anythiing other then trying to help other Mac users.
Depending on how the external drive is formatted there is only one limit and that is to total FILE size, not Folder size. If the external is formatted FAT32 you can't store FILES larger then 4GB. With FOLDERs there is not limit as long as there aren't any FILES inside a folder larger then 4GBs. But no limit to the number of files in any folder.
With the Mac format there is no limit to file or folder size or number of files in each folder.
And with exFAT, a newer Windows format, there is not limit that you would ever have to worry about.
meg in wa wrote:
My MacBook Pro is only a few months old and the internal disk drive is 500 GB. Trouble is my iPhoto library is nearly 300 GB.
What I need to do is go through iPhoto and delete unnecessary photos. But since I do NOT have the time or ability to do that , I need a different solution.
I like the idea of copying the old photos over to an external drive.
*How can I do that???*
Related question: for folders on an external drive, is there a limit to the number of items (like individual photos/movies) allowed in each folder?
Thanks for the help!
🙂 Meg
P.S. Leaving the country in a couple of days, so need this figured out soon. 😉