I had my private pilot for less than a year and fewer than 140 hours when I bought my M20J in may. I did have about 16 hours of complex at the time and was working on my instrument. My insurance was still around $2,700 for $150K hull coverage! I was able to add $1M smooth after my instrument rating for around the same $$.
I felt that getting used to the Mooney was fairly easy, even with low time, and finished my instrument rating in the plane. I would encourage you to take your instrument training in your new plane and would definitely encourage the rating if you are going to fly with any regularity (and you should). I already have 110 hours in my new plane and am loving it.
Good luck, James!