Grab a copy of Mixing a Musical. It’s probably the best book on the subject.
Just picked this up after seeing it recommended in the technical theatre subreddit (or maybe it was here…?): Mixing a Musical: Broadway... https://www.amazon.com/dp/0240817591?ref=ppx_pop_mob_ap_share
Musical theater mixing is a completely different animal than mixing live bands, and one that can seem pretty intimidating if you haven't done it before. For a bunch of reasons, musical theater is typically "line mixed" on the console DCAs - in general if a character is not currently speaking/singing, their mic is not up, which means you are basically throwing a fader for each line in the show. Once you get used to it and pick up a "flow" it can be very rewarding and a great way to learn to listen critically in a new way.
If you're on an X32, you can use u/holty24's excellent software to program the DCA automation: https://jamesholt.audio/x32tc/
Shannon Slaton's book is sort of the go-to resources for theatrical mixing.
Here's a YouTube playlist with examples of the line-by-line mixing technique.
Here are some Signal to Noise podcast episodes with theater sound mixers:
Ep. 54 Kevin McCoy ( u/kmccoy ) and Adrianna Brannon (Hamilton). Here is a video of Kevin explaining theatrical sound mixing to Adam Savage
Ep. 80 Elyssa Kohen (Frozen, RENT, School of Rock)
Ep. 106 Mike Tracey and Daniel Lundberg (Book of Mormon, Jagged Little Pill)
Ep. 114 Carin Ford and Anthony Jones (Hamilton, Mamma Mia, Beauty and the Beast, Les Mis)
My humble contribution (I recently had to do it in Italian, yikes) https://youtu.be/z3Hk3\_CoPTc
You've got the right idea.
Learn DCA/VCA first, that will be biggest improvement.
Then get into scenes after you understand that. Don't do too much in scenes at first, just mutes and VCA assignment.
And read this: https://smile.amazon.com/Mixing-Musical-Broadway-Theatrical-Techniques/dp/0240817591