Whats the size difference with all the wires? How do i know what i need?

02 3.4L

It doesn't really matter much on these engines. Typically a larger diameter wire will have more insulation, therefore more resistance to shorting out. The larger wires may also be able to handle more current, depending on how they are constructed.
If you haven't seriously modded your engine, it really shouldn't matter.

Exacty. If you aren't running any power mods on you motor any plug wire will work fine. I'm using the MSD wires because they were cheaper than the AC Delco wires, that and they are red and my car is maroon. AC Delco plugs, wires, and coil are probably the most durable parts on the Alero. The size of the wire really wont affect anything on a stock motor.

Thanks guys, my engine is stock, no mods. How much does a delco plug go for anyways? Ballpark figure.

Any last little tips or tricks before attempting the plugs?

Just the obvious ones: Make sure you have the correct size spark plug socket, and several different extensions, and maybe a universal also. The front ones are a breeze, the back ones are bad. Label the wires as you remove them. You may want a source of compressed air, as dirt and sand tend to fall around the spark plug heads. Blow it out before loosening the plugs so it doesn't fall into the engine.
I would recommend checking the gaps on your new plugs before installing them, as they can be off quite a ways sometimes.
It's been a while since I've bought plugs, but it should be less than $5 each I think. Good luck!

The Ac Delco plugs that I'm running were around $7.00 US each, or are you taking about how much plug wires cost.

Not to much to changing the plugs, you might break a few taking them out. I have done that a few times.

Wow, where on the plug did they break? How did you remove it after it broke?

Just the porcelain, the white part of the plug. The other half still unscrews.

Thanks rusty. I will start tonight or first thing in the morning. I purchased Ac Delco platinum plugs, here in Ontario ,Canada they came 2 in a pack for $17.89 I only had a choice of 2 wires, i went with the Bosh wires, they were $57.99 they were the more expensive out of the two.

How important is it that i change the wires? I know the plugs definately need it, but i dont want to replace the wires if i dont have to? What should i look for?

I guess it depends on how many miles you have. GM says that their plugs and wires are good up to 100,000 miles. I have around 122,000 miles on mine and I have changed the plugs and wires around 4 times. I would change the wires just to be on the safe side. I had misfires when I ran the Bocsh wires.