One: I have to upgrade my RAM, which is easy.
upgrading the RAM because you're adding more drivespace or replace the drive? absolutely not! though more RAM is better, it doesn't have any effect on the HDD (size, speed, model, whatever).
Two: I have to update my BIOS.
maybe. while bios upgrades never hurt, your computer seems to be new enough to deal with the drives you're throwing at it. i'd try without any updates and update if there're any problems. Dell surely has a very nice site which holds lots of bios updates for their machines.
If you email me include [WIMSBIOS] in the subject.