You DO need the grease! It should be applied to the back of the pads, in between the pad and brake caliper. The high frequency vibration of the pad to the caliper is what makes the squeeling sound. If you never used grease and have no squeeling, you just got lucky. Most of the time your pads will squeel without grease.

A C-clamp is helpfull but not absolutely necessary. Once the caliper is loose, you can move it clear of the disk and then remove the pads. When you are ready to install the new pads and put the caliper back over the disk, firm hand pressure or even pressure on the inside back pad with a small peice of wood is sufficient to retract the piston....just make sure your brake resevoir cap is off. A Haynes manual is helpful, or just check around here for tips. No other special tools are needed, although a borrowed or rented torque wrench may be a safe bet.