My 12 month old lab has started showing signs of becoming a dreaded teenager!  He growled ( I think for the first time in his life) last night at a bitch! he is also very interested in lady scents!  He is still fully in tact.  Is this a phase that dogs go through?  He is still very obedient (he has been going to classes since he was 11 weeks old) I just don't want to lose any obedience if possible.  If he will grow out of it how long can this take?

Yes, this is normal. The 'teenage' phase lasts for about 6 months or so, and it may seem as if a lot of the training you've done has been for nothing, as he becomes a git! But if you can hang on in there he'll come out of the other side similar to how he went into it. Good luck!
:)

Will this be the case even if I don't have him castrated?  he will still just get over it? thanks for your help.

Yep - he will grow out of it even with his testicles intact!
:)

Oh good ha ha! I don't want them off - they are a part of him! I will suffer the tantrums and tiarras with him then for the next 6 months.

How nice to hear somebody whose taking on their dog 'warts 'n' all' - good luck to you - I'm sure he'll repay you 100 times over :)

Thank you Digger.  I am sure he will.  He is my pride and joy and we have a mutual respect for each other so one good turn deserves another don't you think!