I have a 99' Blazer 4x4 and had the left front hub changed about a year and a half ago. I am getting the same Vib. from the other front now. If I was to replace it myself what am I in for and do I need to have the front end aligned again?

Alignment is not necessary. You will have to remove caliper, rotor, and axle nut & washer. Then unbolt the hub assembly off the steering knuckle. You will have a wiring harness coming off the hub for the ABS wheel speed sensor.

Thank You, I will give it a try