To be honest, you might get better value with a casting lesson. Good casting is hard to learn from a book or video.....books and videos are good for people learning how to teach others to cast but they are really hard to learn casting from. Check out free web resources and go to a bookstore/library and read a chapter or two there. Sexyloops.com is a good web resource. You could have problems with your power snap, timing problems, having a mismatch between the line/leader and the size of your fly, etc, a decent instructor could sort this all out for you in a hour lesson. Check your local TU or fly shop.....many often have free casting clinics.
As far as equipment goes, to help with turnover (your problem), you could consider the following:
1) Overlining your rod (put on one line size heavier). This would do two things. First, it would cause your rod to flex more while casting which in general allows you to feel the line load which is very helpful in getting good timing. Second, the increased mass of the line would help turn over larger flies. Most rods really can handle two, maybe three line weights.
2) Consider a long bellied, traingle taper-like line....cortland long belly, rio selective, orvis superfine/easy mend wonderline, and Wulff TT/ Wulff TT long belly lines would fall into this category. These lines have a larger amount of mass at the rear of the belly.....this promotes good energy tranfer down your line to leader to fly.
Now, both of these suggestions will reduce your ability to shoot line somewhat, but we're talking fishing not a distance casting competition. They will also help you be able to mend well also, which is just as important as casting IMHO.
If you still want to get a rod, get one that feels good and that you can feel load. These tend to be longer, more moderate action rods, but each caster has their own groove. Try several out.
