I think it all depends on the program, how their orientation is structured, and where the service is located. I say these things as an opposite point of view as VFlutter, and some of this may be based on different locations and such.
Some places are just like VFlutter stated and want you to walk in the door and knock it out of the park, and if you're not up to that standard then they will interview until they find someone who is. Other programs want a solid level of competency but don't expect you to know everything coming in the door. If the service is located in an area where it is really difficult to recruit people with solid critical care experience it's often difficult to interview multiple people who are going to be performing on that upper level. This is where you will find places that are willing to hire for personality AND that solid level of competency but aren't expecting you to perform in a scenario with a balloon pump for example. I personally believe in the second type of system. The learning curve for critical care is steep and takes time but everyone has to start somewhere and there's alot of flight programs out there who miss out on great provider's because they weren't willing to take a chance.
I personally would rather precept someone who has a good background and is excited and willing to work hard and learn vs. someone who thinks they know everything there is to know about CCT and medicine. I have oriented 15+ people to different HEMS programs and often times the second type of provider isn't anywhere near as great as they think they are, or doesn't stick around long.
With all that being said HEMS positions are competitive, and you want to be on your A game but be honest about your experience. I would much rather someone say "you know what I haven't had alot of experience in RSI" for example than try to upsell and pretend to know what they're talking about and fail miserably. The first person is going to be honest and willing to accept teaching points, and likely work very hard to meet the bar during an orientation, and the latter is likely to have a difficult time accepting the harsh feedback if they ever were to get picked up somewhere. Thus why I prefer honesty.
Study up on all your standard ACLS and PALS type stuff. If you do or know about RSI that is a huge plus. Basic ventilator management, management of common type CCT transports such as head bleeds, aortic emergencies, trauma, shock, etc are all going to be fair game. Depending on the service the written could be extremely hard, or basic, so prepare for the worse there. I personally have never walked into a clinical interview where an A-line, SWAN, IABP, etc. has been present and I got grilled on it, and have worked at some fairly high speed places. I would also be prepared for some operational questions as well. Example: "Tell me about a time when you were on a call and something didn't go so well and what you did to manage it"? or "The sending MD and yourself have a disagreement on the treatment of an IFT patient, what would you do"?
In closing I don't love the saying "hire for personality and train for skill" because you do need to have a good amount of experience and knowledge coming in the door to be successful, but I do like "hire for personality and solid skills and we/I will train you to be great". Good luck, try to not be nervous. Take a few good breaths before you walk in and just be yourself. It sounds like you have a good amount of time under your belt and varied experience, I'm sure you will do well.