there are many options for m4/3 bodies, i have used EPL1, EPL5, OM D10 all are great.
the first two don't have a view finder, EPL1 is old, EPL5 have a new version EPL7 with wifi connection, but both are very small and not comfortable to handle even for a person with very small hands like me.
OM D10 is an excellent choice as the other more professional OM bodies, currently i am using the top end OM DE1.
for lenses i have tried both the Lumix 100-300 mm, and the new Olympus Zuiko 75-300mm.
the only reason i stopped using the Lumix is that is stopped working. so i decided to get the Zuiko, and i wish i got another Lumix.
both can produce excellent IQ, and at 300 mm on a 4/3 sensor this means 600 mm equivalent in the full frame.also there is an in body digital digital teleconverter, which makes 300mm = 600 mm, that is 1200 mm on the full frame.
the Lumix has a fantastic OIS, worked well with me, and also one stop faster.
the Zuiko, don't have the IS, but the in body IS of the Olympus cameras is superb. this lens is better for videos, but i have liked the IQ i got form the Lumix. not much difference, and honestly both are good value for money, compact you can take them with the camera with you everywhere.
hope that helps. here are some results i got with the lumix
and some results form the Zuiko