I didn’t go along the grades route myself, though I had lessons for years, and bass was my first instrument on my BMus course.
I did a Rock school instructor course module in the final year at uni. Some of the more advanced grades would require some serious practice to accomplish. You can buy the books from Amazon, it might be worth getting one or two and read through them, before deciding if they’re for you.
You might also find that you’re playing songs and styles of music that you don’t have a connection to. That’s not necessarily a bad thing, but how serious do you want to take it? Have you got time to devote to it?
It might just be better to seek out a good teacher and study with them.