vehicle has 80,000 miles slight slight leak found on garage floor. advised that cooling system freeze out plug is leaking, suggested that all plugs be replaced which involves removing the transmission to get at the plugs. cost $1,200 plus to do job. Does this make sense? Thank you for your input.

vehicle has 80,000 miles slight slight leak found on garage floor. advised that cooling system freeze out plug is leaking, suggested that all plugs be replaced which involves removing the transmission to get at the plugs. cost $1,200 plus to do job. Does this make sense? Thank you for your input.
This is a very rare problem specially for a 2001 model. Ask to another garage to replace the defect frost plug and at the same time to take a look for the
condition of the others one to see if they could need to be replace. But forget about removing the transmission to replace the one that is/are behind,
if nothing is leaking from there. However, it is important to keep your coolant in good condition ( periodic replacement) to prevent corrosion from the inside of the engine.

Had a block heater develope a leak in my 2000 3.8. Unit was installed in freeze plug bore in the front of the engine, the side closest to the radiator. This plug is fairly accessible, removal may be the hardest part. Expandable aftermarket plugs should be available. Is coolant concentration
enough to prevent freezing? Would only repair source of leak at this time unless garage is aware of some internal plugs that could allow coolant into oil.

What side of the engine is the leak appearing on the garage floor?

You could have the famous "Y" pipe or the "Crossover" pipe coolant leaks (2 separate issues).

I know from experience that the "Y" pipe leak shows up on the passenger side of the garage floor.

Very tiny pin hole leaks develops in either of these two components and the small amount of coolant leaks down to the block which may make it appear that a freeze plug is leaking.