The .243 will work fine for whitetail. And it's a great choice if you're adding coyote as well. Can't help you on the needing a mentor thing. I would suggest possibly looking into some hunting clubs, outdoor clubs, etc and maybe through that you can meet people. Also, if you are on Facebook, look up groups in your area.... As an example... The group "PA Black Bear hunting" has over 3,000 members. And I have met people to hunt with through that. Bear hunting is a little different, in PA allot of people put on big drives so they are looking for people to come out and hunt, but a group like that may open doors for you.
-Jake