It shouldn't really matter which way the pipes go on, to be honest if you have put them on the wrong way round it will probably flush out more crap anyway.

Wouldn't worry about the tank not getting hot either, just so long as it isn't overheating, you have nice hot heaters etc then everything should be ok. Take it for a run, leave it ticking over for a few minutes and feel both radiator pipes. Just so long as they are nice and warm then you shouldn't have a problem.