Being as collaborative as you can be is a good start. Outside of that, being honest and transparent about why the changes are happening is a good way to build trust with the new team. Keeping a positive attitude and energy around it will also help to soften the blow. Most importantly, continually ask the new team for their feedback along the way. This will help them to understand that while you are implementing new procedures to help things run "your way," you still respect and value their opinion.

Best of luck!

That is always difficult. In my experience that can be a killer in a small environment in many ways. I suggest dealing with it quickly and honestly. Do you see an opportunity for the person to adapt or is there no hope? Sit down with the person outside the office to have a genuine conversation about your concern and hear them out. It may be appropriate based on the outcome of your discussion to give a certain time period to allow them to implement your feedback, or it may be best to part ways quickly. Either way, always remember that leaders get the behavior they tolerate, good or bad. Nipping this in the bud will help the team members who are a great fit see you value their input and keep them motivated.

Best of luck!

Congratulations on making it this far in the process. If this is what you believe is truly the right fit for you, continue to pursue them while you wait out the 5 days. Politely, but assertively, reach out to let them know you are still here, interested, and ready.

I also think your age and in their words "inexperience" could be an opportunity for you to play up you energy and coach-ability. The most attractive trait I like in a leader is the ability to be coachable. If you can show them that you have the energy to learn the things you might lack quickly, because you are coachable and willing to take feedback, you might win them over. Being coachable means proactively asking for feedback, then quickly implementing what you've heard, which with you fire for the job, should be no problem.

Hope it goes well!

Great question. The simple answer is honesty. But to be more specific, polished honesty. As someone who has done all levels of recruiting and contracting, honesty takes you a long way.

A few tips: regardless of why there was a gap (let go from a job, bad situation, went back to school etc.) remain positive. We love to see what you learned or were able to take away from your experience.
Also, don't exclude failures from the conversation. Don't make them the focus of an interview, but I loved to meet people who acknowledged times when they had failed, showed me how they learned from it, and most importantly how they overcame and moved forward. Failure is a great learning tool if you choose to see it that way.

Don't let a gap in your resume hinder you from going after what you really want. The worst you can hear is feedback on why you might not be a great fit. Take it constructively and prepare for something that will be the right fit to propel your career to the next level.

Good luck!