Yes, a competent independent shop, specializing in Audi's, can certainly perform the timing-belt replacement work. In most cases, the independent shop will provide the parts below the dealership prices and their labor charges usually undercut the dealership labor charges.
Due to the "major-surgery" nature of the Audi timing-belt replacement (the technicians have to open-up the entire front-end of the engine to gain access), it's prudent to perform a number of other parts replacements that require the same degree of engine-bay access. So, in addition to the timing-belt (and it's related components), it's considered advisable to also replace the water-pump, thermostat, etc. since these parts will likely fail before you're due for another timing-belt.
* 2003 A4 3.0L Quattro (6-speed manual)
* sport package
* 18"x8" Moda MD5
* Continental ExtremeContact DWS (235/40ZR18)