Good for you. Welcome to MOTOBRICK
This rescue may take some time and $$s to bring it back to the fun, reliable machine it is.
Beside replacing
all fluids and most likely battery and tires you will want to inspect the fuel tank closely.
Lots of good information on all of these topics and more on this site.
Keep us updated on your progress and what you find. There are many years of Brick wrenching on this forum.