So, my boss and I have had a rocky relationship from the start. While he recognizes my ability to get what he needs done, he likes to micromanage my progress, which I do not respond well to. It's a small business, and new legislation has created an emerging market for him to corner, and corner it he has. He's counting on me to help him with the production in this, and I have spent the last month streamlining it, getting which was originally a 10 hour build down to 2 hours per unit.
After three months of this sour relationship, I started actively job searching again. Three months into search (six months into my current job) I am scheduled for an interview with a company that would put my college-earned-skills to much better use (I could have done my current job fresh out of highschool with the same results).
I'm not trying to count my chicks or anything, but if this new job does pan out, I have to take it. Aside from the possibility of a boss with whom I may have a better relationship, it's much more in line with my expertise and from the tone of the job listing I may start out at nearly double my current salary, the company also offers insurance and benefits that my current employer doesn't, and probably can't.
This is an office of three people (me, the boss, and a programmer). If I leave, it will basically kill their workflow. I'm not going to be as brash as to say I can't be replaced, but it would take my boss/coworker valuable time to get someone else trained and settled into my position; this could potentially cost the company hundreds of thousands of dollars. I just would not feel right about doing that.
TL;DR
My boss has a big project in the works, I may be leaving my company, I want to offer my help with this project. I figured I'd offer to come in, week days or after hours, help with the actual assembly/configuration of the product, and possibly train my replacement to perform the task in the streamlined fashion I've developed.
When/How is the most professional way to offer this? Should I bring up the subject of compensation for my time?