Yep, gift giver needs special attention! Do the salmon first! Then clean the grates completely! Some people swear that fish will “contaminate” the smoker, I have never had an issue after cleaning well.
As for the brisket, as a long time member, who has become an international friend and co founder of the “Order of Hephaestus”, told me:
“Put on your big boy pants and just do it!”
Forewarning, you will likely not sleep well if you do an overnight smoke, you may be able to doze if you start it at the crack of pitch dark 3 AM, you will worry and fret over the thing until you realize what I told you before “It will be done when it’s finished!”
Side note, no two will ever cook the same! I have had two briskets of the same weight and trimming take sixteen hours and the second one was done in nine! I posted that drama last summer. PM me if you want my account of the hilarious surprise story at 6:00 AM