CB45DX same as CB45N ?

Hi all just wondering, i bought an cb45dx for running back and forward to work, theres some confusing on a manual for it, but i was told that a workshop manual for a cb45on is basically the same, is this true?

Also i have noticed that the gasket seems to be going theres some oil leaking out after a short run, the oil is coming out between the crankshaft and the cylinder head, is this a big job? is it a sign that something is about to explode? any advice would be welcome thanks.