It really is a peice of piss mate.
Lets assume your mobo will support over 137Gb without a BIOS update or new card fitted - you can do this at a later date if you need to (will have to format again though)
Take the case off.
Check for physical space to fit the drive.
Set the jumpers on the new HDD to SLAVE (see the picture on the drive)
Decide whether it is going as primary slave or secondary slave (i'm assuming you have your CD or DVD on secondary master)
If primary then take your other HDD out and make sure it is set to MASTER (not cable select)
Put old drive back in
Put new drive in (if in a 5 1/4, attach brakets to drive first)
Connect IDE and power cable
Start PC
Go into windows, it will auto detect your new drive
Go into My computer, right click the drive and choose format as NTFS
Job done!
If it only displays 137Gb of space then go looking for a BIOS update and if not available, grab one of those IDE controllers.
As for the memory... make sure the connectors are open, insert the memory (right way around - will only fit one way, check where the slot is) You may have to push quite firmly, the plastic clips normally snap into place.
^^ Don't think I missed anything there.