The best advice I can give you, is to go look for the hardware manuals for the machine on the manufactures web site. You are looking for a hardware maintenance manual. It will give you information on how to remove the HD, the new one goes in easy enough when you have the old one out.
The hard part is knowing how the machine is assembled with screws that can be very difficult to find.
You are correct, a new drive will be 'bare'. You will need to partition the drive, then format the partitions, and then install. Been a long time since I used any flavour of buntu, as I remember it, there are partitioning tools, and formatting tools on the install .iso. I would recommend you make a / partition, a swap partition, and the rest for /home. You can make it more complicated, but it will run just fine like that. Separating /home and / allows for easier installs in the future.
Post questions, if you have them.