I've been the proud owner of a rather nice Dell 1545 with an internal CD/DVD Writer for about six months, but I'm finally succumbing to the call of Blu-Ray.
So, One - is it possible to replace the internal CD/DVD drive with a blu ray drive (either BD-R or for preference BD-RE) and Two, if I were to play movies on it, would the laptop's processor have the grunt to handle it? I opted for the Pentium processor (forget which model) which is a 64-bit dual core, so I'm hoping "Yes."
Yes, the drive can be replaced. If you have the ATI video chip, you should be all set. If you have the Intel (which cannot be upgraded), not so much.