"How difficult is it for a fingerstyle player to learn electric guitars and be able to play Blues Solo?"
They are very different styles. Like learning to play flamenco style, it's a big jump. I dont want to discourage you, but I do want to give you an idea of what you are dealing with.
"I only play with thumpick and three fingers and never learn to play with a pick. And I am very new to scales etc."
This is country style, usually only with two fingers (thumb plus two). Blues style is very different from this, no fingers, and using only the pick to change volume and timbr (making notes into music.) Bending notes is critical if you want to know this style. You know this from your 4 finger country style, but the bends have moved, as have the way you bend them to get blues style.
"I personally feel that learning online lessons could be a better option then going to private classes…Anyone "
You defintely need to see someone play it. If you know bluegrass style,(I think you do) you need to see the other style played, nothing else will give you good idea of the techique.
There is also a technical side - looking at harmony and such with bent notes, and so on? - but that's another thing to look at later.
I have have a lot of respect for country style, it's not easy. This is a completely different style though.