If those older files are only 300k then they are little more than thumbnails.
Unless you have a very broad broadband connection I don't think the iPhoto Library is suitable fr online back up. The amounts of data being transferred is just to large. We have seen people on here complaining about restroing taking several days just because the amounts of data are so large.
Further, as most such services are sitting on disks formatted for other systems, problems can arise restoring the library as the service doesn't understand the structure of the iPhoto Library.
As to how you get that amount of data:
The iPhoto Library consists of various thumbnail, original and edited versions of the photos, database files and caches. All are required for iPhoto to work. The specifics depend on whar version of iPhoto you actually use.
You are very wise to consider off-site back up. FWIW here's what I do:
My Library lives on my iMac. It’s Backed up to two external hard disks every day. These disks are permanently attached to the iMac. These back ups run automatically. One is done by Time Machine, one is a bootable back up done by SuperDuper
It’s also backed up to a portable hard disk when ever new photos are added. This hard disk lives in my car. For security, this disk is password protected.
I have a second off-site back up at a relative’s house across town. That’s updated every 3 or 4 months.
My Photos are backed up online. There are many options: Flickr, Picasa, SmugMug etc. However, check the terms of your account carefully. While most sites have free uploading, you will often find that these uploads are limited in terms of the file size or the bandwidth you can use per month. For access that allows you to upload full size pics with no restrictions you may need to pay.
Every couple of months I test the back ups to make sure they are working correctly. It’s very easy to mis-configure a back up application, and the only way to protect against that is to do a trial restore.
