The stabil track light came on on my 2010 Buick LaCrosse. The codes that come up are U0073 and U0100. Can you tell me what I need to fix my car?

U codes are communication codes . You won't be able to fix this , guaranteed . Your best bet would be to take it to a buick dealer .
The serial data circuit is the means by which the control modules in the vehicle communicate with each other. Once the scan tool is connected to the serial data circuit through the DLC, the scan tool can be used to monitor each module for diagnostic purposes and to check for diagnostic trouble codes (DTCs). When the ignition switch is in RUN, each control module communicating on the serial data circuit sends a state of health (SOH) message to ensure that the control module is operating properly. When a control module stops communicating on the serial data circuit, for example if the module loses power or ground, the SOH message it normally sends on the serial data circuit disappears. Other control modules on the serial data circuit, which expect to receive that SOH message, detect its absence; those control modules in turn sets a DTC associated with the loss of SOH of the non-communicating control module. The DTC is unique to the control module which is not communicating, for example, when the inflatable restraint sensing and diagnostic module (SDM) SOH message disappears, several modules set DTC U1088. Note: a loss of serial data communications DTC does not represent a failure of the module that set it.

U0073 00
Control Module Communication Bus A Off
U0073 71
ECU HS Bus Off
U0073 72
ECU LS Bus Off

There are 2 different communication networks on this vehicle: The class 2 network and the GMLAN network. The class 2 serial data circuit is the low speed link, and the GMLAN serial data circuit is the high speed link. Modules that need real time communications are attached to the high speed network. The engine control module (ECM) is the gateway between the networks. The purpose of the gateway is to transfer information from one network to another.

012 GM Class II Communications

001 Welcome to 20 Years of Communication Networks for Imports and Domestics

002 Introduction to Communications

016 CAN Communications