By multifunction switch... you mean turn signals, wipers, high beam switch...? If you find it locally it'll prolly be around $100, probably less.... not too sure though. It might be a PITA to get at though.
Multifuncion switch (MFS) is a piece of cake to replace but is is also easy to repair. I would geuss that some of the features are not working as intended by your question.
It haaaas been a while but here is the routine.
Disconnect battery, remove ignition swithc, remove steering column covers. THere are two cannon plugs and 2-4 screws to remove the MFS. At this point you can replace with new for about $45 (I think) or try very carefully opening the MFS (2 screws I think). Be very careful as you pull it apart, there is a wire bewteen teh 2 I had to resolder.
If you look at the electrical paths they are probably coverd with green stuff called verdigree which is normal corrosion for copper. You acn clean up the verdigree with a pencil eraser and q tip with rubbing alcohol.
What is wrong with the MFS? If you are having problems with the flashers/turn signals, see maceslin's post above. If you are having problems with the various wiper/washer settings, you just need to clean the contacts in the end of the turn signal/wiper stalk. It takes <5 minutes, and there is no need to remove the steering column covers or any of that stuff. Here is a link to an old post about this. If you scroll down a bit, I posted instructions on how to clean the switch up.
Lucky, I had the exact same problem with my MFS like 2 weeks after i got my taurus. I went back to the dealer i purchased it from and they replaced it. I had a warranty so all i had to pay was the $100 deductible. They were also kind enough to include the map lightbulbs that seemed to be missing from my car. How silly of me...i thought those would've come pre-installed