Most likely just a 10mm wrench/socket and a pair of good pliers to deal with the hose clamp at the bottom.
Pretty straight-forward operation
NOTE: be sure the engine is COLD before opening the reservoir tank!!
NOTE #2: if the anti-freeze is good/fresh, you can catch it in a clean container when you take the hose off, and reuse it / put it right back in when you're done
On a 2002 Mercury Sable : The engine coolant reservoir is at the front of the engine compartment , on the passenger side of the engine compartment ( the engine coolant reservoir has a thread on cap on it , that is your pressure cap / radiator cap )
I was looking at a picture in the 2003 Mercury Grand Marquis Owner Guide and it shows the power steering fluid reservoir at the front of the engine compartment between the engine coolant reservoir and the engine air filter box
Coolant is used to keep an engine in a vehicle at a temperature safe for operation. If no coolant is in the reservoir, an engine will not start.
On a 2002 Mercury Cougar : No , the thread on cap on your engine coolant reservoir is the pressure cap / radiator cap
The thread on cap on your engine coolant reservoir is the pressure cap / radiator cap on a 1999 Mercury Mystique
The ENGINE coolant reservoir is on the drivers side of the engine compartment next to the firewall
No , the thread on cap on the engine coolant reservoir is the pressure cap / radiator cap
The engine coolant reservoir is in the engine compartment , on the drivers side , near the firewall
On a 1996 Mercury Sable : The thread on cap on the engine coolant reservoir is the pressure cap / radiator cap
The thread on cap on the engine coolant reservoir is the pressure cap / radiator cap
The thread on cap on the engine coolant reservoir is the pressure cap / radiator cap for the engine cooling system
On a 2003 Mercury Sable : The thread on cap on the engine coolant reservoir is the 16 PSI pressure cap / radiator cap