its hard to advise without knowing the full details. But there are some points I can make, qualifications and ability are two different things. On the basis of political experience I'm not qualified to be President of the US. But I believe I have the ability to do the job (at least better than the incumbent

).
So the question you need to ask yourself is whether you think you can do the job, not whether you are qualified to do it. Your partner seems to think you do have the ability if he offered it to you.
As far as displacing someone who may be more qualified, I wouldn't worry about that.