Cgc is not a bad way to go the only other professional grader that I would look into is CBCS. Its actually started by the guy who started cgc. Cheaper, faster they authinticate signitures. Quickly catching upto cgc. Avoid PGX or any other service. As their grades are junk. I run a comic book store and If i have a PGX graded book people pick it up then go "o its a pgx" and set it back down immediatly after looking at it. CGC obviously is market leader. Tried and true.
I just sent 20 books to CBCS before all the covid stuff. Im waiting on books myself. I would call CGC and make sure they are accepting books before sending.
Also be VERY picky. The first time you send books in you realize how strict their grading is. Which is a good thing.