Help with website migration...

Hello, I run a small business in healthcare. We have grown recently and are looking to improve our digital marketing.

My partner founded the business and built the website back in 2015 through Vistaprint... I came on board later and have since familiarized myself with the Vistaprint builder and have tried my best to make it look as good as I can design wise, and as of right now it ranks ok on google. My issue is that I know I could build a much better website in Wordpress, and I know in the long term it would help significantly with both SEO and user experience. The Vistaprint editor is extremely limited in what you can do, and the site as a whole has an amateur feel to it as a result...

I want to migrate the site to wordpress but I'm at a dilemma here as I don't want to tank our current rankings in the process... Our website ranks OK, but the bulk of our traffic seems to come from our Google MyBusiness listings, as we show up in the top 3 for our targeted keywords in the google pack... I think this might be a good thing (?) as if we do take a slight drop in our website ranking, we'll still have our Google MyBusiness pages visible...

I could use a bit of guidance about this. This problem is only going to get larger as we continue to grow. I feel like I definitely need to make the switch this year, before we undergo another big expansion, but I'm unsure of how to actually go about it.

She purchased the domain through Vistaprint as well and I'm not even sure how to transfer it to another registrar.

What are some things I should be considering before making this switch? It doesn't need to be done immediately, but as I said I'd like to get it done some time in the near future.