Many new lecturers asked me what to do if they are asked to teach courses that they don't like or they don't have expertise. My standard advice always 'take it, grab it, don't complaint'. It's part of the learning curve. What do you expect — smooth sailing? "A smooth sea never made a skilled sailor". To me, as an academic, it's important to get a broad-based knowledge and at the same time specialize in a few subjects (maybe a bit later). So, it's a kind of "Jack of many trades and a master of ONE". Holistic, maybe?