These are both trivial tasks, but you will need to change your attitude. I think this fear of mechanical things is not uncommin in many women, and related to 'math anxiety.' The key, is to approach it logically. For anything you want to do mechanically, just look at it, ask yourself how it works, and then it will be obvious what you need to do. For example, pedals, all you need to do (with the right tool) is loosen the old ones until they come off, place the new ones on (with grease of course) and tighten. One trick though, is that the direction that tightens is not the same for both pedals. Here, to reason it, ask which direction do you need to turn so the pedal so it tightens rather than loosens as you pedal.

If you are new to mechanics, I recommend buying a book to walk you through things, like the park tools blue book or Lennard Zinns the art of road bicycle maintenance (I have both). They'll also explain the non-obvious, such as when to use lubrication, what kind, how much, etc.). Its all really easy, especially the tasks you asked about.