I hope it is just angle of the forkVframe but I think you fork is bent. Try looping a rubber band around the down tube and hook it on the valve stem. The take a good look at the fork from a right angle to the bike. The upper painted section of the blades should follow the line of the head tube angle the curve forward at the chrome section. This one looks like the blades angle back a bit.
That Diamond Back decal looks like a old BMX decal. Is that a dent on the top tube?
Personally depending on you definition of 'restoring' this may unfortunately be a bit too far gone. It certainly needs a doo deep overhaul (all parts stripped from the frame everything cleaned regreased and reinstalled), tires, tubes, cables, brake pads, bar tape maybe a chain too.
All that can add up. if you can do the work that will bring the cost down but depending on how nice a tires and cable you use parts can run $40ish to 100+. If you can't do the work the labor may run $100-150ish depending on your location.
Are you a avid cyclist now? If you put $100-200+ plus into this will you ride it? I really wanted my Dad's old guitar and was going to have it cleaned up but the odds of learning to play were slim.. so my sister got and she actually took lessons.
(for all you geetar nuts I think it is an old Martin from the '50s. He used to sing in a local country band)