Windshield replacement is, generally speaking, not that hard. I have only done a couple (not on geo though) and one of the important things is to get the proper window sealant. I got mine at NAPA but I am pretty sure you can get it at just about any auto parts place. It is specifically made for windshield installations. I cannot remember what it is called but ask at the store and they will know. You also have to buy a wire knife to cut out the old one.
If you can get it done for $100 you might want to consider that. You can certainly do it yourself but it can be messy and if you break the new windshield during the install there goes your savings. Your auto insurance company also might cover window repairs 100%. Mine did and I did not even know it.
If you decide to DIY, it would be cool if you posted some pics on the forum as you go.
Best of luck