Hard to believe you want to swap piano black interior trim for myrtle wood. I know looks are subjective, but that is nuts.
I had the piano black on my '01 325i and wouldn't have traded it for anything. Last year for that trim in the E46 - if you do swap it out, don't be doing any straight-up trades with anybody. Most people don't want the wood trim - you could probably find some for pennies while selling your black trim for considerably more.