how can I fix an uneven hydraulic disk brake set
In my view its unlikely the entire brake needs replacing, although if you have to pay someone for the time needed to resolve the problem, its entirely possible it will be the cheapest solution in the end. 

As already said in comments, the most likely cause is contamination of discs and pads with brake fluid. If the pads have been cleaned, the next step is to replace them and thoroughly clean the disk.  

Another possibility is the shop replaced the pads with new ones. In this case there are a couple of possibilities. It may be the new pads just need to be bedded in, and the problem will resolve itself with a half dozen high effort stops. You may also need to replace the pads on the other side with a matching set as different pad material have different characteristics.