Depending on your level, you could do a lot worse than start with the "Hard Training with Mike Gratton" thread on the FLM section of the Forums. At worst, almost any of the regular posters there can answer your question, and more than a couple of them are coaches themselves.
This question has been posed before on different boards and there has been some pretty mixed response to one-on-one coaching. The jist of it has been that the better, and more committed you are, the more you will get out of it.
Running coaches are not, generally, like personal trainers. Personal trainers tend to take on all-comers for a sum of money and that's their job. Running coaches, on the other hand, are often part-time and tend to like to work with people for whom running ranks pretty high on life's priority list and are really less interested in the back-markers. There are obviously exceptions that prove the rule, but that has been the majority conclusion from what I have read to date.