Crustychief is definitely steering you right here! Just a couple of things to add, though:
Make sure that pressure is applied to the window but not
too much. Too much pressure in the wrong spot will crack your window. Take it easy and apply steady pressure along the window closer to the seals.
We use 16 gauge wire. We put it in the seal as crustychief mentioned, but we use two pieces of wire instead of just one. Start with an excess of wire (maybe 2-3 inches) hanging out from the top middle of the window rubber. Push the wire into the gap and go all the way around (patiently) until you get to the middle of the bottom of the window. Leave 2-3 inches of wire that hangs out and cut the wire. Do the same thing to the other half of the window leaving the 2-3 inches of wire extra at the top and the bottom. The excess wire from one half needs to overlap the excess from the other side a bit in the seal because that is what gets the rubber of the seal to pull up and over the lip of your window opening. If you can, put a little dish soap over the wire once it's laid in the rubber so it will come out easier.
A good buy would be a suction cup for windows - this gives you a way to pull a bit from inside if you need to. It also gives a little extra holding power when the window gets messy from soap.

No one ever tells you what a pain it is to get the new rubber on the window. Dish soap around the edge of the window will help get the rubber on and will provide a little extra stick as it dries. Patience is definitely a MUST. Make sure you get the rubber on the right way - the thin, flatter part goes outside with the grooved, thicker part going inside. I can picture it in my head but can't seem to get the words out right this morning. Ask me questions when the rubbers come in if what I've said here doesn't make sense and I'll clarify.
This is a lengthy process so I would say to do only one or two windows at a time. Cut out one old one and install the new rubber onto the window and then install the window. If you've got time, do another. If not, wait for the next weekend. Do your leaky one first and go from there.

There is absolutely nothing written that says you have to get them all done in a day.
Again, I may not be explaining well so please ask questions. It's one of those things where I can visualize it, but getting all the words out completely (pre-coffee) seems challenging today.
You can do this. And you can save a TON of money by doing it yourself. The dealer or a shop will charge an arm and a leg because it is time consuming (for more tha one person) and there is a risk of window breakage (we've done that!!).
Let us know how it goes whenever you decide to do it!!