Is there a way that I can attach an internal hard drive and not have it become part of the filesystem but still accessible for both read and write?. Additionally, how can I take same hard drive and format it to ext3, I haven't ever done this before, so any help would be appreciated!

You can create partitions on the disk using fdisk, then format the partitions as ext3 using mkfs.ext3. As for reading and writing to your disk, you will need to mount it manually when you need to read or write to it so you need to create a mount point for it somewhere in /mnt or /media.

If you have attached a internal hard disk drive(hdd), assumed you already have a hdd installed with linux, your internal hard disk drive will not be auto-mounted and "become part of the filesystem". When your system starts up, it will read the configurations from /etc/fstab and mount from there.

So what you have to do is to manually mount everytime, unless you add the lines yourself into /etc/fstab so you do not have to worry it will "become part of the filesystem". Read more about fstab by typing man fstab, man mount.

You need to format your hard disk drive using fdisk, create a partition then you can make file system(mkfs) on it, to make ext3, just type mkfs -t ext3 <device-partition>, type man mkfs to find out more.