Low voltages are not dangerous and these power supplies do not usually go high voltage and damage anything.
The +5 is the main voltage and preferably need to be close to 5v.... 4.92 is about as low as i like to see it. +12 i like to see 11.9+.
recapping might help the psu,but there is adjustment inside for +5,but if memory serves it will also affect +12,so check both when adjusting.