Huge electrical job

So we have a huge unexpected expense coming right now. Because that outlet in the kitchen had smoked around the time the dishwasher was being fixed, it hasn't worked since. The other day, I heard a whirring sound in there like high electrical activity going on behind the outlet. Anyway, we turned off the breaker to the kitchen so the power was out to that box, and Nate pulled off the outlet box and found that there was a small electrical fire that happened. Needless to say, we've found out that the whole house was wired wrong by the idiot "fix and flippers" and it is not to code and not safe. The whole house has aluminum wiring (since it was built in 1969) and it is attached directly to the GFI. This is not safe because it can easily overheat. It needs to be pigtailed to a copper wire. So we had two electrical companies come out to give us a quote. They are both good so we will pick the less expensive of the two. But it is looking like it will be at least $4,800 (up to $5,400). This is a HUGE expense and a HUGE chunk into our savings accounts (which are already running lower due to me not working as much). So I guess I'm asking for any advice anyone has. We are trying to contact the fix and flippers and the realtor that sold us our house...since they did not honor their contract to fix the aluminum wiring before they turned the house over to us. So in all honesty, we should not have to pay. But I know this is the real world. Any advice in this stupid problem?