How do you replace the drain pump on a Bosch Washer?

I have a Bosch WFK2401 washer and the drain pump is making a lound rattling noise. We already removed the filter located on the machine to see if we could feel an obstruction, none there. I was able to get the machine to finally drain, but it does a load or two and just stops with an 03 code, meaning a foreign object in the pump filter. Again we drain, open the filter and nothing there.

What I can't figure out is how to open the machine up to replace the entire drain pump and can't seem to find a repair manual from either Bosch or on the Web.

Can you suggest an alternative or let me know where I can find out how to do this?