I am interested in using Gmail via Google apps for my domain. I have had success with the emails but not with the website portion. My question is would it be possible to only use Gmail Google Apps as opposed to migrating entirely to Google?
Absolutely. You can use only the Google products you want, and leave the rest unused. It is merely a matter of DNS records.
For using Gmail, you need to set the correct MX records. If you don't want to use Google Sites for your website, you don't have to do anything else - your current website will stay unchanged, while your Google Sites will be available at http://sites.google.com/a/yourdomain.com
If you want to completely disable Google Sites (or other Google Apps services), you may do so from the Google Apps control panel.