How to change spark plugs on Ford Contour V6?

I want to change the spark plugs on Contour (98 V6).
People and book say that the plugs might break in
the hole. I want to save the money (dealer wants $260 labor
only to change plugs and wires).

I do some repairs all the time but never changed plugs.
The 3 in front seems easy but the rear 3 seems hard.
I have 3/8" wench and spark socket.

How to remove them safely? How to reach the rear 3
in right way? What should I care about?

Thanks in advance.

Jian