Warlocks are a little bit tricky when it comes to macros and targeting. the whole target target system might not work with the warlock as well due to this one spell... drain life. otherwise, i think it should be fine. what drain life does is it actually targets the mob that its draining life from, so if you use the targettarget sytem, then you'll actually change targets upon casting the drain life spell. this works fine until you want your warlock to target another target, in which case, you'll need it to retarget your main, then cast its spell. otherwise, most spells will work. you will probably end up using the focustarget system, as it will always target your focus' target, and you'll always have one focus, as opposed to switching targets after a drain life. i suggest starting with the focus system. just a caution though, if you plan to CC using focus, then you're outta luck as your focus will already be your main. but thats not crippling to gameplay at all.

specs should not have any affect or effect on macros. also, stick to the same specs. i find it very hard to play as two different specs. if you want, you can just make them both hybrid specs. but i dont know, whats right for me will probably be totally not right for you. so play around with the specs if you want.

as for mods, i'd wait on that since 3.0 patch is going live. but i'd pick the following: shardmax, xperl, dottimer, a buttons addon like bartender or trinity and onebag as basic. necrosis works well also, and can replace your dot timers, shardmax, and buttons addon all in one.