Speaking very generally, I think you're at an advantage switching from upright to electric rather than the other way around. I played upright for a couple of years before I ever touched a bass guitar, and all things being equal (that is, playing primarily walking bass lines), the transition was pretty seamless. I just copy/pasted my Simandl 1-2-4 upright technique over and it worked fine. My teacher recommended trying to play some of the classical pieces I had been working on BG in order to learn the fingerboard better, and that helped a lot.
When I started exploring some the extended techniques (slapping, chords, etc.) is when the challenges of BG became more apparent.
Even so, back when I was playing a lot more BG than upright, I would need a week or so to get back in shape if I got called for an upright gig. Now, playing much more upright than BG, I can make the switch to BG with little preparation.
Pull up the weeds before they're too damn big.