Well a PML is only adding shackles and an AAL in the rear and cranking the t-bars in the front. It shouldn't take that long to do it maybe an hour or two at the most but that would be if you are doing it for the first time. They should be able to do the work with no problems.

I know that you said that your dad wants to get a warranty on the work which I guess is the install but not sure if or how they would warranty anything if a part broke. You could always save yourself the money and do it yourself or do a mod day.