I've cooked select/ungraded that turned out as well as any prime brisket I've ever purchased. The grading is pretty much irrelevant for brisket, no matter what the guys on TV say.
That said, I just picked up a 13# prime packer from Costco for $4/lb. Beef prices are definitely up right now.
I'll be smoking it, along with some pork spare ribs and a couple chickens, for a big "Eff You Covid We're All Vaxed" Memorial Day weekend shindig at my house on Sunday.
Oh, and regarding trimming a brisket-- don't worry too much about it, just remove any really hard chunks or discolored bits.