Car Troubles: part 2 (or is it 3!?!)

Well, if you haven't been keeping up with my car troubles here is a link to where it all started.  We did get my car in (and out) of the shop and it is now running beautifully; sadly, the same cannot be said of Chris' Kia.
The day we got mine out of the shop, in went his to have his brakes worked on.  $535 later his brakes are quiet and stopping the car! 

We have since decided that my car (the Ford Focus) would now be the "family car" so whoever has Will will be driving that one, and Chris' car (the Kia Rio) would be the "commuter car."  Since this is my week to work I am driving the Kia.  I have no problem with that.  It is sometimes fun to get to drive a standard.  I just wish it had a working radio because the thoughts in my head annoy me at times. 

Anyway, back to the original topic.  I was driving home yesterday (in the Kia) and noticed that there was HOT air blowing at me.  Not cool-ish, not lukewarm, just plain HOT!  So, I decided that while it did suck big-time to not have AC in the 111 degree weather, it would be cool soon, and we would just deal until we had the money to fix it.  Yeah, we can deal for a couple of months.  About that time the car started shaking and making a weird noise and the check engine light came on.  Two things I know for sure about cars:

1.  Don't drive it with no oil.
2.  It is not supposed to make the noises I was hearing.

All that to say we have our car in the shop yet again.  I am just dying to know how much this is going to cost us.  This is definitely an eye opener for us.  I thought an $800 car sinking fund would be plenty.  Well, obviously I was wrong, so we will be increasing it just a bit.  I think $2000 ($1000/car) will be a better goal.  What do you think?