If money is not too much of an issue I recommend Norton Ghost it can be bought and downloaded on line.
Ghost will enable you to transfer the entire disk to a new disk, if it is your system disk it will make the new disk bootable (I would say it's an exact copy but it will transfer a smaller disk to a larger disk).
Documentation is pretty good.
Physically attaching the Disk is pretty straight forward too, all disk manufacturers will have details on their sites:
Replacing a hard drive is relativly easy.
JUST BEWARE OF STATIC WHEN WORKING INSIDE CASE
The fit is usually a slide into a spare bay and secured by small screws.
you will have 2 connections - power and cable to motherboard.
The cable will probably have two black connections, the master drive must be fitted to end furthest from motherboard.The slave will be in middle connection.
In your current set up you might have your existing hard drive on master and cd/dvd player on middle as slave - in this case you will need a cable for new drive- these are usually supplied with drive.
The key is getting your jumpers set up. these are a set of pins on the back of the drive, by moving a tab or switches you can set your drive to be master or slave.
Now your current hard drive will be master on either ide 1 or ide 2. what you want to do is set your new drive up as a slave on either ide, copy your information from old drive to new then set your new drive up as master and then remove old drive.
You will get information on setting up jumpers either in documents that come with drive of on manufacturers web site e.g.