if(christophercalm_is_gone) {
follow_his_instructions();
}
On a more serious note though, on a social level, I think «if I'm gone» is much better phrasing than «when I'm gone» if the intention is to be prepared for unforeseen tragic events. Unless one is facing a terminal illness or is past a certain age, using when is too melodramatic, especially when the target audience are close loved ones. It doesn't only imply the inevitability of being gone some day, but also implies the certainty that ones current loved ones will have to face it and must know what to do.
I imagine that the author hopes to live to a ripe old age and probably outlive his "somewhat complex" home setup. In that regard, the if makes more sense, as it is nowhere near certain that anyone will have to deal with his home setup when he is gone.