I have Adobe CS3 Extended as a standalone program.
What happens when I install the new CS4 Suite? Will I lose my special features? Adobe should install all CS4's new features while leaving CS3 "Extended" features alone.
That is exactly what happens. CS4 is a complete new program and will not do anything to CS3. Also, Photoshop CS4 is the version of Photoshop that is included in any of the CS4 suites that have Photoshop - you have some bad info as CS3 is not included in CS4 suites - it is a different program.