It depends on what kind of learner you are.
If you have good buoyancy in a wetsuit, don't have any problems getting your weight dialed in, like to read manuals thoroughly and like to learn skills on your own, you might be able to skip the class.
If you plan on renting a drysuit you may have to show a drysuit cert. You might get by if you show a bunch of dives from your log using a drysuit but that won't be good enough for some shops.
If you are a learner that needs the advice of an instructor to learn new dive techniques and how to care for your drysuit, you will probably get a lot out of taking the class.