挑战自己一把

I think first you can get as much information as possible regarding the requirements and responsibilities of these positions. You may have a clearer picture what parts you are qualified at, and what you might struggle with. Is your doubt about your capability based on your experience or your perceptive? Generally speaking I would like 挑战自己一把. You don't always have the opportunity. Grab it when you can. What's more, you will learn a lot more at a higher position, though you may have a hard time in the beginning.