tonight i replaced the corroded negative battery cable, and when i went to start it up i saw a flash in the engine bay and the ignition light went off, now the lights don't turn on and it doesn't crank, what did i fry? my multimeter shows the battery has juice, i think the cable is connected properly because i put the tester lead on the bolt that holds it to the block.

my friend suggested i get a v8, i said no, i'm hooked on the slant!

Probably a blown fusible link, which is the main circuit protection, a special wire that runs between the large terminal on the starter relay and the bulkhead main electrical disconnect junction. It's got a tag on it that says "FUSIBLE LINK" or "FUSELINK". But, it blew for a reason: something's drawing massively excessive current through the main feed. Dead short somewhere. You're going to have to fix it or the new fuselink will blow straightaway again.

_________________
一期一会
Too many people who were born on third base actually believe they've hit a triple.

If you're lucky, it may just be a badly oxidized connection that made a slight contact that then fried. That's an easy fix.

Check using a test light (or a DMM w/ a load) whether you've got +12V from the starter relay post to engine block (not the battery cable). If you don't, the problem is before the link and probably easy to fix. If you do see full voltage, follow Dan's advice.

In that case, I'd 1st check for a shorted alternator. A cheap trick is to put a small +12V light to bridge the blown link and start disconnecting things. When the light goes out, you've removed all large loads. (Don't forget to disable the dome light, as it's a load too.)

it was the simplest thing possible (aka something i can fix), the positive cable to battery post connection