Welcome to EAB marvio.
First things first, Goal! > Sensible Soccer!
The A3000 has a built-in SCSI controller so you'll need an SCSI HD. Installing Workbench is quite easy, you'll just have to execute the installer from the install disk and follow the instructions. Nothing too complex.
About Lightwave, there are versions you can use and install w/o toaster.
Hope that helps. Have fun with your A3k, it's a nice machine!