It is impossible to tell you how much a fix would be if you don't know what EXACTLY is afoul.
Engine coolant consumption could be something as inexpensive and simple to fix as a leaking EGR spacer gasket or intake gasket(s) or as expensive and complicated to fix as warped cylinder head(s) and or block.
A "slipping" clutch could really be a bum cable, a quadrant on it's way out, a gouged release beraing retainer and or bad release bearing, glazed clutch disc and or flywheel, etc.
You're going to have to dig into the problem areas and figure out what exactly is needed.
1979-1993 Fox Capri and Mustang VIN Decoder: foxchassis.com
Wanted (Dead or Alive): VINs, Vehicle Certification Labels, Buck Tags, Build Sheets, Window Stickers, Owner Cards, Warranty Tags, History 999 Reports, Invoices, Axle Tags