Funny you should ask... I just had one of my MD55RLTs in the sink for a detail cleaning earlier tonight. Yes, you can take out the screws on the front of the pump. This will allow you to take off the cover (with in/out tubes), impeller, and the little gizmo that the impeller sits in. Lets you clean it real good. I'd also recommend taking off the cover at the other end of the pump to clean off the fan. Yes, you can remount the cover with the output rotated. As for mounting it vertically, I'm not sure on that one.
I can't say if it is right or wrong, but I had my Iwaki mounted vertically for over a year with no problems. It was bolted to the stand leg. As long as you don't block the fan (if it has a fan), my opinion/experience would be that you should not have any problems.