;)
There's a lot to do on the I-90 corridor. If you're new to the backcountry, I would ideally try to find someone who knows the area you plan on skiing in and have them take you out. Then they have a pretty good idea of where to skin up, what areas are avvy prone and the best lines that they might be willing to share with you. If you don't know anyone, then a guide service is also a way to get this info.
CalTopo and slope shading is your friend.
There is also this: https://www.amazon.com/dp/1594856567/ref=cm_sw_r_cp_apa_i_TA9BFb77ES449
Lookup Yodelin, Litchenberg, Jim Hill, Skyline Lake. This book has everything to get started https://www.amazon.com/Backcountry-Ski-Snowboard-Routes-Washington/dp/1594856567
For backcountry:
Take AIARE level 1. AAI, as well as a bunch of other outfits, offer this class.
resources for backcountry travel: