Memory usage:
I have 2 SME systems running and both hover at approx 99% usage. One system has 512meg, the other has a GIG. I don't have extremely long uptimes but I've never had any problems with things not working as memory usage increases. It's working as designed - as others here have stated.
Updates:
Go to any of the download mirrors and look for an updates folder for the version you have installed. There will be installation instructions there also.