assuming you have a 986, if you have access to an independent Porsche specialist with a good reputation, the basic job of just swapping the old IMS bearing with the the new LN unit is not very complicated even if you're specialist is doing it for the first time. A couple hours to remove the transmission, a couple of hours to remove the old bearing and swap in the new LN unit, a couple hours to put it all back together and replace the oil.
If your car has high mileage you'd obviously want to take advantage to do some other work like replacing the clutch and servicing the axle boots, putting in a new flywheel if it looks shaky. So you figure 10 hours total if you did all of the above. Maybe 8 if you only did IMS bearing. Over here on this side of the ocean my specialist charges $85 an hour. Basically $800 on labor and another $1,000 in parts and fluids. It was his first time doing this procedure so he had to buy the special tool to easily extract the old bearing. But all in all for a shop familiar with disassembling old 911 engines this job was elementary. Incidentally I had a dual row bearing from the factory that was tip top. I was a little worried because my car had only taken on 9,000 miles in the first 4.5 years, so it sat in the garage a lot but when I took ownership we changed all that.
I sorta regret waint as much as 9 months to change the oil but I now do the oil changes at least three times a year no matter the mileage.