I'm not personally familiar with the Olympus product line, but I looked up the specs and reviews of the E-PM1 and 75-300mm lens. They seem to be reasonably priced with reasonable features and quality. The E-PM1 has the necessary capabilities to shoot wildlife provided you don't expect too much out of it. Also, the PM1 is targeted at "beginner" photographers and has minimal mechanical controls. You'll have to get familiar with the menus to set it up properly.
The Olympus 75-300mm lens gets good reviews for image quality at the 75mm focal length, but not so good at 150mm and higher. It also has a fairly small maximum aperture (f/6.7 at 300mm) and no image stabilization. How fast it focuses seems to depend on who's reviewing it.
If you want image stabilization (I would), check out the Panasonic Lumix G Vario 100-300mm f/4.0-5.6 Zoom Lens.
I use Canon gear myself, but believe that what's behind the camera is more important than what's inside it. I've seen many people use expensive equipment to produce mediocre (or downright poor) images. High-end DSLRs don't take better pictures unless you understand when and why to use the settings they provide. Expensive glass isn't a magic bullet either - I've seen good and bad photos from both low and high-end lenses.
Until you learn how to use your camera, and understand exactly how its limitations are holding you back, there's really no point to spending more on fancier gear. More money won't automatically produce better photographs.
I hope that helps,
Eric
