Does anyone know the latest OS with updates, etc. and where to download it for the 8300?

It's hidden in the stickies at the top of the 8300 series forum. Be sure to select the one for your specific model.

Other than plugging some leaky memory, are there any other fixes/benefits to upgrading?

Thanks very much everyone.
If I get stuck at some point I will check back ok?
Does it matter what the carrier is, or just the model of the phone?

Just the phone model. As long as you delete the Vendor.xml file you're good to go with any carrier's OS for the 8300.

Not quite sure where the file is or how to delete it.

Once you download the OS to your computer and install it into the BlackBerry Desktop Software, you will find the vendor.xml file located in c:\program files\common files\research in motion\apploader.

The instructions (including location of the vendor.xml file) are in the sticky at the top of the forum. Follow the instructions exactly as written and you should be good. If you don't, well expect problems.

Read the Latest OS thread for the release you're considering. It will contain the best info available to answer that question.