My Bessie(1976 240D Euro.) won't start by itself . HELP!

My alternator belt broke. I replaced the belt and I also replaced the glow plugs.

I've only had the car a few months...Now
the car won't start up without me spraying THRUST starter spray for diesels! Then it starts right up. If I let it set for a few hours. It won't start up again. The glow plug light had already stopped coming on.
Is this serious? I had thought I could get this car together maybe doing alittle at a time but now I don't know. I may have taken on too much.
My instrument panel does not light up. The gas gauge doesn't work. It drives great. I love it. It does have a little knocking in the front sometimes when you're waiting at the light. Sometimes when going up the freeway ramp. It won't have as much power. Other times it flys up there. It doesn't smoke that much. So no problem there. It doesn't use oil or get hot.
I enjoy working on cars. If I have the proper instructions. I can pretty much do a lot of things myself. Since I've had this problem I've been considering maybe selling this car and getting another one. A newer model. Or just one in better shape. I know I have to put it in the shop for some of these problems. I hope someone out there can help me with some of these problems. I really don't like being blind when I go to a dealership. I would like to kind of know what's going on with my car.
Thanks in advance, Loretta