Howdy Vid, Have you goten a full rotation out of the engine since you replaced the head?? and if so try to take the head off and spin the motor over and look at the cylinder walls looking for scratches vertically.

But no its not hard to change the engine, the hardest part is breaking it in.. Oh and maybe changing the clutch and flywheel.

And hurry up with this check as you have a trip to go on soon, so time IS of the essence!!