Trepidation on dressing

Today I go scuba diving in Lake Pingvallavatn, (I think it is spelled but definitely not pronounced that way). Yesterday I drove by the lake on my tour and saw a van there with divers but only caught a glimpse of them so could not see how they were dressed. OK, I am a scuba diver, I have a 100 or so dives completed, and I've never had a problem getting on my swimsuit, my wet suit if needed, and my scuba gear. But as the guide said yesterday, this lake is very, very, very, very cold. The diving is done with a dry suit. Until a few months ago when my divemaster was wearing a dry suit in the Florida keys, I had never even seen a dry suit and today I must put on one. well, hmmmm. I was told to bring long underwear and warm socks. I have both. I also have a scuba skin which is kind of like scuba underwear. I asked my husband what order I should do this, swimsuit, scuba skin, long underwear OR swimsuit, long underwear, scuba skin. He responded with an article that said you really don't want to wear much at all under your dry suit so maybe I wanted to forgo to swimsuit!
Luckily the people doing the diving are well used to hand holding and making sure their divers of woefully pitiful dry suit knowledge are helped along, I think. They have been emailing the answers to all of my questions. Just wish I had thought to ask them how to dress before they come to pick me up this morning. I might be changing out of my swimsuit in the back of the van and it's really, really hard to put on my scuba skin without a lot of arm flailing and wriggling and jumping up and down. I'm sure it will be a very interesting day.