Welcome. Looks like your purchase has lots of potentials. Yes, there will be much to do but enjoying the E34 makes it that much more fun to work on it. Start with going over your cooling system. A word of advice, you never want these to overheat or come close to it.
Your friend should point you in the right direction but explore this site and educate yourself by reading the helpful posts from everyone here.
Example, I'm about to replace my thrust rods (upper control arms) and have been reading and educating myself on the process. Looks like it can be a PITA so I'm learning as much as I can from previous posts of others before diving into this project. Did the same back when I completely rebuilt my cylinder head, VANOS, brakes, cooling system, and lately, replacing the driver's door latch.
Good luck and looking forward to your progress pics.