When I created the blog I've choosen under SEO permalink schema "Use extra-path: year, month & day".
I'd like to change this into "Use extra-path: post title"
Before I am going to do this, I'd like to ask you, whether this would cause problems with meanwhile search engine index of my blog and what you would recommend.
Thanks in advance, Will
Your old URLs will still work and redirect to the new URLs. So you will not have broken pages at any point.
However, it is difficult to say if redirecting 100% of your URLs to new URLs will have 0 impact on search engines. I personally move very cautiously with this sort of changes.