The way I read MGN 156, following the flowchart on Page 12 is that if you have have your STCW 95 Basic courses, AEC and ENG1 and provided that you have either:
36 months service as a dual purpose deck/engineer officer responsible for the
maintenance and servicing of the vessel, whilst holding an AEC certificate; or
24 months service as a yacht engineer responsible for system maintenance whilst holding an AEC certificate.
You should be able to apply for an Notice of Entitlement to sit your MEOL Oral board at a MCA office of your choice. You will need passes in the following also before a Certificate of Competency will be issued:
Proficency in Survival Craft and Rescue Boats (PSC & RB)
Advanced Fire Fighting (AFF)
Proficiency in Medical First Aid aboard Ship
I believe the engineering craft skills training test is for folk who don't have an AEC as they may be exempt, ie ex military like me or ex diesel fitters.
When you have your MEOL you will need another 12 months sea time (as an engineer) and another oral exam to get to Y4
I haven't come across any PDF's for Oral preparation having looked before I took my Y3 oral in August last year. If you can afford it I can wholeheartedly recommend taking a few days prep with a specialist who knows the 'pet' questions of the office where you are taking the exam. If you can further afford to come to the UK to do it I can recommend whom to go to.
I'm fairly current on this having waded through it myself recently, I think I have it correct! Any further queries, let's have 'em.