The 1985 Accord SEi had a fuel injected ES-series engine, I'd assume the manifold fits your engine, unless you have a CVCC engine. A CVCC engine will have a 3 barrel carburetor and won't work with the EFI manifold. Do you have a down draft carb or two side draft carbs? I have no idea if the EFI manifold fits the engine with side draft carbs, it might. Are you sure the engine doesn't already have an 02 sensor? Most 80s carbureted cars had them.

I don't know of any instructions for carburetor rebuilding, even the factory service manuals don't have that. But I've taken them apart before, they're pretty simple to deal with. By the way, a factory manual should be less than $20 on eBay.

Besides Majestic, there's also HParts and San Leandro Honda for parts. I've ordered parts for older Hondas from HParts a few times with no problems, they have always had every part I needed. Good prices too.

There should be a sticker on the underside of the hood with the timing specs, but just sticking it where it drives the best has worked fine for me.