To replace the DVD or add a blueray drive:
Turn off the computer and unplug it.
Open the case.
If you add, remove one of the front plates. Most of the time, you don't need any tool for that.
If you replace: disconnect the original drive and slide it out from it's bay.
Slide in the new drive, secure it in place. With the actual cases, you should not need any tool.
Connect the new drive.
Close the case and reconnect, boot up the computer.
Normaly, you can keep the original drive.
Your new blueray drive may not be able to burn CDs and DVDs, for this reason, I suggest that you keep the DVD RW unit.
You may need to install some new blueray capable softwares to be able to play bluerays medias.
You won't need any new drivers just to access CDs and DVDs.
As you have Windows 7 installed, you should have the required drivers already present. Windows should recognise and correctly configure the blueray drive. If needed, windows should automaticaly check online to get any needed driver.
If not, you'll need to insert the windows install DVD when prompted.
Be warned that you need a blueray capable monitor to play blueray content. In fact, the blueray specifications demand that the reader, the computer's motherboard, the video card AND the monitor all be fitted with special, costly, blueray decoding and protocol negotiation chips.
Electro, December 2011