Lever for hot/cold water not turning to full capacity
are you talking about the shower mixing valve?  if so, they have an internal bushing with teeth that can be pulled out and turned, then put right back in to allow for hotter water.  check the instructions that came with the new valve for adjusting the water temp. you'll just need the appropriate size allen wrench to take off the handle and a philips screwdriver to remove the bushing to turn it.
low pressure could be a number of issues.  If you have a pressure reducer, a couple turn to shorten the screw could add some pressure for you.  also could be solder stuck in the pipes if he didnt flush them out.