2000 Challenger Engine(s) Issues

[blackfalcon]

I aquired a 2000 challenger that my inlaws had loaned to my sister in law. When I got the boat, I figured it had the crankshaft seal issue. I blew the oil out of the left engine... (this oil was color of oil in resevior. ie not dirty at all), and there wasn't that much of it. The right engine, which they said was having the issue, had quite a bit more oil, but this oil was black and very dirty. Ie no the color of what was in the resevior. I can get the left engine to run fine, reve up etc. The right engine would never run anything other then a rough idle. While trying to get it to run, I noticed that it had a crack in the rear engine cyclinder/block towards the top.

My suspicion is that my brother in law, ran boat on left engine for a while and never drained/blew out, etc. the water from right engine that built up(manual warns against towing with engines off) Hence the cracked cylinder, because it probably froze in the winter.

If I pull the right engine, and replace cyclinder block, should I also be digging deaper, or will I have to put the engine back together and see what issues crop up. Ie the dirty/black oil in right engine, does this cause anyone to think of something else I need to explore further as well.

What's the best place to get a cylinder, and are there any DIY writups on engine removal/crankshaft replacement for these boats.

Thanks