Are there any complications when replacing the leaky rear seal?

Which seal are you talking about, the pinion gear seal at the front, or the cover plate on the back?

Cover plate is usually no big deal, drain the oil, pull the cover off (sometimes you have to pull the cover off to drain the oil), scrape all the old gasket off then install the new one. Before you install the new one line it up with the old one and make sure that it has all the same holes as the old one.

Pinion seal I would let a drive line/rear end shop do.

The seal is the right rear at the wheel.