You definitely want to speak to someone with experience in dealing with addiction - particularly benzodiazepine addiction, as a GP might wean you off too quickly (or too slowly) and it could take far longer than it needs to. They will more than likely refer you to a drug and alcohol abuse clinic, where they'll ask you for a urine sample, interview you about your drug-use and your goals, and then write a tapering plan and a script for you to collect regularly.
The first thing they'll do is switch you to a benzo with a long half-life, like diazepam. This means that the highs and lows will be a lot less bumpy and violent, and you'll feel far more stable. It's typically a 2mg/14 days sort of deal, so expect to be tapering for a long time, but ultimately slower can be better for this sort of thing. You might want to quit quickly, but that's foolish, 'cause you'll experience a wide range of emotions and it's important (IMHO) to work through them with plenty of time.
If you have any questions in particular about withdrawal from benzo's after long-term abuse or anything related to benzo's, I've quite a bit of experience with them. Poke me on here and I'll try to respond when I have some time!