Yes, PRELIMS is a Scrabble word!

Letter values in Scrabble US: P 3, R 1, E 1, L 1, I 1, M 3, S 1.

Is it a valid word?

PRELIMS is a valid word in the official Scrabble dictionary (US), the UK Scrabble Dictionary and Words with Friends (ENABLE).

written matter preceding the main text of a book
a minor match preceding the main event
an examination taken by graduate students to determine their fitness to continue

Also: front matter, preliminary examination, preliminary exam.