don't be afraid of this job, seriously. It's not bad at all, and depending on which harness you want to replace, would only take a few hours tops. engine harness could be replaced in an hour or so. most everything is done with plugs, that only go to their correct counterpart. you can just label each plug as you unplug it, and when things go back together, just look at your old harness, and you'll know what went where. Very little to no chance of fire. ground plugs won't plug into positive plugs.
I had a 78 Trans Am years ago with every possible power option, and the entire dash and engine harnesses were totally hacked. I went down to pick your part, found another 78 with a good harness, labeled all the plugs as I pulled them out. I brought it home, and by the end of the afternoon I had everything up and running like new.
an electrical shop might really stick it to you price wise for a job that after you do yourself, you'll know how your car goes together a lot better than you did the day before.