Call your local parts store.
There isn't a 2010 Mercury Cougar in North America
Assuming you mean Mercury Cougar, a new 1983 Mercury Cougar sold for $9800.
about 300
45.00 dollars
Check for the recall on that. I believe it is recalls.gov
I had the same problem in my 1999 Mercury Cougar, I replaced the flasher located in the blinker assembly. It was very simple to do. Flasher cost about $10
The most common problem for the 1995 Cougar xr7 Transmissions is the shift selenoids and the TCM Transmission control modules needing to be reprogramed common fixes for the shift control module would be a transmission overhaul or replacement do to the fact of the shift control module is located inside of the transmission and as well another cost effective fix is to get the transmission control module reprogrammed.
Get aftermarket, shouldn't cost no more than 100 each. One on front of manifold, one on back of manifold and one in the back.
About $60.00 for the switch. Kind of hard to get to under the car. Need a tool to align center nut in neutral though. For 94 Cougar tool number is 307-351 (T97L-70010-A).
$49.00 - $89.00
A head gasket itself is only about $15. I live in nebraska and if you were to get it professionaly fixed, it would cost anywhere from 200 to 500 dollars..
It varies with what part of the country you live in. Call a couple of local garages for estimates.