I have the same exact mower and it just started leaking. I've had it for about 9 years now. Do you have the part number for that gasket! So glad I found this video! I thought the block cracked!.
Remove the bolts and a few taps on the cover with a soft face mallet did the trick. Some covers you need to drive out the locating dowels, others can stay in. This one used hollow locators and they were fine to leave in.
Cost will always depend on your shop rate. This one was really quick and I had it back on the mower within a couple of working hours. There was also the setup time for the sealer and we did a quick turnaround for the customer which is worth something too.