Join Date: Jul 2002
Location: Vineland Ontario
Don't replace just the one coil, do both sides. It isn't necessary to change the fronts out - unless you're going to adjust the height by putting in lowering springs, or adjusting from a stiff to a soft spring or the other way around.
Even though you're financially challenged at the moment, you could try junkyards for springs, they aren't worth more than $20/piece.
As for safety - don't worry about it. Keep an eye on them in case more coils break. Right now it'll sit a bit funny on the one corner, and you'll probably hear noises. Alot of people here have found broken springs when they've gone to change components, including myself on my little brother's SC, both rear springs were broke.
About labor - you can change them yourself easily enough if you have jack stands and a floor jack, so that won't cost anything.
1992 Mercury Cougar XR7 5.0 - Rust In Pieces
1995 Mercury Cougar XR7, rust free Florida car - future 5.0 project