Happens to every one of these cars...question answered here http://wiki.answers.com/Q/What_is_the_easiest_way_to_reset_the_needles_on_the_fuel_and_temperature_gauges_on_a_1997_Buick_Park_Avenue
Yes. They will also be lost if the battery drops below 12v.
The fuse box for a 1998 Buick Park Avenue is located just below the dash near the driver's side floor board. It houses most of the essential fuses required to operate the vehicle.
Under the dash below steering Column behind a plastic cover
driver side, mounted directly to side of engine block, below exaust pipes.
remove cloth trunk liner, u will see taillight wires and recepticles right below.
Trouble code P0128 means:Coolant thermostat (coolant temperature below threshold regulatin temperature)
On my 2000 Park Avenue, it's right in front of the radiator just below the hood latch mechanism. - GEO
The transmission connector is right below the battery it could have been knocked loose.
top, driver side, of lower part of the intake manafold. directly below throttle cables and air intake tube.
Should be locate on left front fender well, behind battery, below air intake tube.
The 1999 Buick Park Avenue has hook-end wiper arms. See related links below for installation videos. Press the tab or button in the area where the wiper blade is inserted into the hook and pull the wiper blade out of the hook. Sometimes you need to rotate and flex the wiper blade a little bit to make enough clearance.
It should be 118 ft/lbs of torque. I've also included a how to video in the related links section below, if you are unfamiliar with changing them.