Shinerunner and 39

I also have numerous other problems with this car I just tried to start it after it’s been sitting for a few years and it’s completely dead I jumped the starter but have no spark it was converted to 12 V which I believe cause more problems than it fixed the points look good and free of corrosion and oil but all the wires and connections are corroded for the 12 V system any idea where I should start I not even getting power to the ignition switch the horn doesn’t work either which isn’t a big deal but it was one thing that always works the only thing that works is the headlights and tail lights Where should I start

I have a 39 Buick eight and the brakes were leaking fluid and I cannot find any brake reservoir and I also lost my clutch well I lost all my brake pressure somebody told me that it is in the floorboards on the driver side there’s a small panel that I can’t figure anyway to get it up without damaging my car what is the best way to go about getting to my brake reservoir thank you I appreciate your comments