don't worry about not being sl/sl specced. some of the best pvp locks i know are FG spec. sl/sl is a survivability spec and can be very boring because of the lack of damage you dish out.
that's not to say that sl/sl isn't the 'best' spec for arenas. it probably is but people shouldn't feel they have to spec that way.

I have a 70 sm/sl loc and a 59 FG loc. One on one this will be a tougher fight now, but very possible. The key changes that affects locs are the armor dispel and the reduction of the dead zone.

Put your armor on your action bar and get used to recasting.

Single key macro your instant cast dots, order them so they time out about the same time, so long duration dots first.

If you surprise the guy hit him with an SB or soul fire 1st, dont use D/C or dots right away, get that extra damage in.

If he catches you by surprise death coil, demo sac, dot(s), fel dom a voidy and sac it. Spam SP and DL. And stay away from him, being close to a hunter now serves no purpose.

Oh and if it looks like your gonna win, go ahead and kill his pet 1st, they really like it...