I did my conversion back in 2010/2011. I totally recommend Bristol Ground School.

I personally found Naples Air Center to be disappointing as a flight school, but maybe they have changed since then.

If you are already typed on a 737, I would just avoid doing anything GA and get your EASA license with the 737 sim and training organization. It will probably save you time and money that way. NEDude had a very thorough write up.