Yes, ALTERING is a Scrabble word!

Letter values in Scrabble US: A 1, L 1, T 1, E 1, R 1, I 1, N 1, G 2.

Is it a valid word?

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

cause to change; make different; cause a transformation
become different in some particular way, without permanently losing one's or its former characteristics or essence
make an alteration to
insert words into texts, often falsifying it thereby
remove the ovaries of