If you don't feel much resistance when you turn the flywheel with your finger while the engine is cold is a sign of excess wear.
A hot engine will turn over easier.
As for gooey crap in the engine, that just can't be a good thing.
A bit more information would help in diagnosing that.
There will usually be some oil residue left in the engine and pipe. It likes to drool on my leg when I pick my truck up to look/work on it[X(]...[:@].

Hard to start could be just a glow plug that need to be replaced.