Hi !
I'm happy to see there is a beginner here.
I've been playing the double bass for six months now.
Although I only play jazz, I'm learning with Nanny's Method, it's old but efficient.
Don't be afraid, don't think block and thumb positions are for advance players, just do it.
It can be difficult but it's not more difficult than half-position, it's different.
If you play the bass guitar you've got a big advantage because you know how the neck works.
If you can, watch videos about classical players, I think they are more open-minded than jazzers sometimes, I better say, they go forwards and they explain it with a simple language, sometimes it's not so far from the bass guitar.
Don't be intimidated by the instrument.