Thanks for these great advice.
I was also wondering where that stuff that kept the axle together with the diff went. Looking at the other side it seems like there is supposed to be some sort of plate with a bunch of bolts and probably a C-clip inside there again. I couldnt see any parts on the road where this happened either. I probably just hung on there by the boot...
I am sure it is the original axle, and the odometer says "just" under 200.000 miles, but I am sure the car has done a few more miles than that.
Note that the oil was in the outer joint which was still attached to the car. The inner joint with the diff was bone dry except for some grease. Probably the previous owner did some "hack" to get it to run for a while. He actually did make a note that the axle would have to be replaced before I bought it. So it is not like I walked blindly into the deal
My mechanic would check up on a used axle from the scrapyards, so I am sure he will find a good deal. The new ones run about 500euros here as well.
Considering I paid US$400 (with current exchange rate) for the car it is worth fixing. Cant wait to get it back on the road and get on with some much needed servicing. We just got it and had just done a couple of 100s miles when this happened.
Thanks again for these swift and good answers.