Due to your limited expertise the better approach would be to go with the original parts. Using replacement / equivalant drivers can be done, but there is a lot that you need to learn in order to realize satisfactory results. If a direct replacement is not available or is very expensive, repair/rewind of your existing woofer's voice coil may be possible. Try contacting Van-L speakerworks for further information: they do these kinds of repairs.
http://www.vanlspeakerworks.com/
http://www.vanlspeakerworks.com/