Most drives need some level of prepping (Windows or Mac OS-X) and all need an OS installed.

Sorry to hear your drive failed.

But before you get a new drive you'll need to make sure you get the correct one. Your system supports a SATA II (3.0 Gb/s) drive. Don't get one of the newer SATA III (6.0 Gb/s) drives as it worn't work reliably. You may want to consider getting a SSHD hybrid drive like Seagate's.

The next thing here is prepping the drive do you have a second Mac system or access to one? That will make things easier.

For now let us know what drive you are thinking about and if you have access to a second Mac system and what model it is.

To prep up your new drive you have a few options:

The easiest is to install the drive in your iMac, then connect your MacBook Pro via FireWire cable to your iMac (back to back). Then startup your iMac in Target Mode. Once up and accessible by your MacBook Pro like an external drive you can use Disk Utility to format and setup the partition/s the way you would like to have. Then you can use the Mac OS installer application to install the OS on to the drive. Just make sure the OS you install is the correct one for your iMac.

The next option is to use an external FireWire or USB drive case (or IFIXIT universal adapter) to hold your new drive. Then connecting it to your MacBook Pro. Here you do need to be careful as the desktop drives pull a lot of power so make sure to use an auxiliary power supply as I've seen drives not correctly setup when the power was just on the edge.