Thinking of the funeral, in the end, your ex-MIL has lost her son, even if she is a narc. I had nothing like this at my DH's funeral as all ILs and parents were safely under the sod.
However, in the spirit of offering advice about things I haven't experienced, take it as a dress rehearsal for the later times when support may fall away, as it often does, and no-one, but no-one asks you how you feel. Or says fucking stupid things like are you dating yet?
Fuck I sound bitter.
Anyway, I hope your DH's funeral is a good one, with as many laughs as tears.
Tell us about it if you want to, and when you can.