okay so first off this carburetor is missing a part and so i think i am going to have to get a new one, any suggestions? In Ohio if possible.

second off someone tried to rewire this thing and completely just made it look like a rats nest so I'm thinking about stripping it and buying a wiring harness good idea or bad idea?

and last is there some sort of book on this vehicle to help me work on other things as well?

Can you post pictures of the carb and wiring.
If you can identify what part/s are missing from your carb you may be able to get them, suggest you try Webcon in the UK, I'm not in the US so can't advise a source of carb parts, maybe an internet search will point you towards a US spares provider.
Afaik new carbs are typically c.$250 - $350 if you can find the correct model. It's probably a Weber (Italy) and the model number is usually stamped into the bottom mounting flange.

Wiring loom problem, again a picture would be useful.There's a lot of work involved in stripping out the old loom and fitting a replacement, assuming you can get one. Afaik there are 1 or 2 companies in the US that will fabricate a new loom but they might not do one for the 124 Spider, plus it'll probably be pricey. I'd try to repair the existing loom if at all possible. You didn't say where it's damaged/messed with but parts of the standard loom look like a rat's nest (as you describe it) anyway.

Re a service/shop manual I believe International Auto Parts in VA,USA
www.international-auto.com/ stock a Fiat Spider Workshop Manual 1975-on (Item # 04251) for $59.50.

International Auto Parts don't seem to have carb, carb parts or wiring looms in stock for the Fiat 124 Spider. Afaik there are specialist parts suppliers in the Netherlands and Germany , you can likely find their details incl websites if you do an internet search, which should also give you lots of Fiat parts suppliers in the USA.

Al.