I have ballade sports TCT and notice a leak at the bottom of the base . Is it hard to remove the TCT and replace the two O-ring gasket?

 

Not hard but follow the instructions closely as the TCT has a number of uber slippery internal parts and spring(s). Proper tool is probably a 10mm wrench (like half the bolts on the car). Torque, the bolts, don't guess.

Not sure the age of your TCT but there may be upgraded or replacements for worn internals available. Check with Ballade.

-- Chuck