2001 STS that has 100K. replaced spark plugs and just wondering if I should be worrying about other service at this point such as transmission, brake fluid replacement etc....? Any help is appreacited!
As far as GM engineering is concerned, the Maintenance Schedule section of the Owner's Manual is a good place to start. Everthing else is subjective.
"MY" Maintenance Schedule includes;
brake fluid @ 3 years maximum
transmission fluid @ 100,000 miles (use Dexron VI)
accessory and water pump drive belts @ 100,000 miles
throttle body service (cleaning) @ 25,000 miles or as needed
engine cooling system (Dexcool) @ 3 years or 50,000 miles (whichever occurs FIRST)
Also a good time to flush the power steering system. Remove the cap and unclamp the upper hose with an 8-ounce Pyrex measuring cup underneath to collect the fluid. Then replace with the same amount (probably 6 ounces exactly), drive for a while (or at least start and move the wheels through their full range of motion a few times) and repeat until the fluid you drain looks like new fluid.
If the first fluid you drain is dark, expect to use 3-5 quarts!