You can print it in one piece or left and right parts separately. It's highly recommended to glue separate parts together, if you are printng them separately. The pins are there only to facilitate alignment. You can also use the fastener to keep the parts together.

ABS, PETG and PLA should be fine. I printed with a Eryone Silk PLA.

You can keep the original plastic scews used to secure the original glass shelf. I went for metal screws.

Upd. 1: A hook added

Upd. 2: A fastener added