1. What bobcheese said
2. Possibly, but I wouldn't... the amount you would save would be insignificant, especially if you have problems, or worse, strange intermittent problems later that could be RAM relates. If memory serves me correctly, it is not the same type of memory your average laptop uses, don't hold me to it, but I think it is ECC Registered memory...
Remember that if you are going to upgrade you will need to make sure that your software assurance if valid, otherwise you can't change the software version.