The ideal start is a trial flight, and the instructor will answer many of your questions then. Assume that it costs about double fixed wing and you will be in the right ball park. To get a PPL(H) will take you between 45 and 60 hours on average but you do get let off a few hours for having a PPL(A) already. Yes, you can happily fly both without compromising safety - bit like going to Europe and driving on the other side of the road really, as your brain can cope with the switch between f/w and rotary without a problem.
Others will no doubt point you to much more comprehensive answers on many threads in this forum.
If you do get hooked it will cost you loads but you will enjoy it.