Hi Mark, welcome aboard. As BearGFR points out, don't give up as those days of frustration and wanting to throw in the towel will hit.
You want to first decide what you goal is with your car.
1). Restoration is expensive if you go that route and try to bring it back to original. You will most likely be upside down on this as most restorations cost more than its selling price that you will get should you decide to flip the car. The exception would of course be a rare or unique one-off, or low production car.
2.) Rest-Mod, as we call it, gives you more options where you can change things out for original to make the car functional, and yet improved with such things as suspension, brakes, trans, etc. and retain the looks of the GTO. Resto-mods can actually bring in a good price IF done right, but keep in kind that some add-ons are specific to your tastes and can hurt value - one being the serpentine belt conversion. Any future buyer is probably going to be looking for a car that is more on the lines of original, so serpentine belt conversion costs you money that you probably won't get back. Now if like some of us, you plan on keeping the car forever, then do as you feel.
3.) Get it running, driveable, and safe and have fun with it. I did this with my '68 Lemans so I could enjoy it for a few years, shot a coat of spray bomb primer grey on it to cover the rust & dents and make it one color, and enjoyed it (Rat Rod style). Now I am doing rebuild
#2 which is a frame-off resto-mod. You can upgrade the car and build as you go, but I have done this and its like a cat chasing its tail - you never quite get it done and as soon as you think you have, you are having to go back and work on things you already addresses. It is hard to drive and rebuild your car at the same time. I don't know why people do this, but they take a ratty car, rebuild the engine, then advertise it based on the new $3,500 engine, and then want to get $8,000 for the car, when half the body is rotted away. You gotta be real with what you have. In such cases, do your body work first as this will be your foundation for all other work. If you get dis-interested in the project, you can sell a good body and let the next guy do his thing with it.
4.) Any combo of the above. :thumbsup:
So put a plan together, get a realistic cost of what parts or labor will cost you and go from there. Ask questions if need be and you should get your answer here. There is also a "search" box up there on the upper right which will help to answer questions that others have inquired about. Lot of good "food for thought" there.