i've noticed a issue i believe is in the front end, maybe someone may know what it is;

While cornering there is a vibration/shake in the steering wheel, and can be felt throughout the car, it vibrates worse with speed... its rythmatic and also can be heard. On the highway above 70 mph there is an intermittent vibration every 5 secs or so, and gets worse when the speed is increased.

I've tried to diagnose the problem, and think i've narrowed it down to the tranny, particularly where the cv joints connect to the tranny. there is about 3/8" movement up and down NOT in and out. From this i assume when the cv joints are rotating they are causing the vibration due to being off balance, thus becoming worse while turning and explains why it vibrates more with speed.

Is this a differential issue? if so, is this a diy job?

The car is a 93 civic Dx 1.5L, my previous was a 92 Mitsubishi Lancer Evolution I which i did some mechanical work on, so i have some mechanical experiance.