Iceland in November will be lovely. I've been there a few times both on business and for pleasure.
My first "pleasure" trip was a long weekend with dh in November 2008, just as the financial crisis was starting (the Kreppa as the Icelanders call it), so I ended up having to spend a bit of time doing business (keeping a deal I was in the middle of alive).
We went of on the Golden Circle Tour with Reykjavik Excursions. They adjust it slightly in the winter months to coordinate with the hours of daylight (I've since done the tour in summer): they visit an Icelandic wool/souvenir shop first before going to Thingvellir as the sun rises.
Make sure to wear grippy shoes on the tour as the paths around Gullfoss are sheet ice. But it's beautiful in winter, with ice waterfalls and all the plants shimmering in the frozen mist from the waterfall.
Geysir and Strokkur are also icy as you're walking around - but. Great experience.
We went to one of the newer geothermal power stations at the end of tour when it was dark again. In summer, we went to one of the older ones as the first stop.
I agree about having plenty of warm clothes as the wind can be biting.
The public hot baths are brilliant and great value. You can visit them in the evenings when it is dark and enjoy the weird experience of being outside in your swim suit in the dark and cold
The one at Laugavegur is the biggest but there are plenty in Reykjavik.
Just be warned about the (single sex) changing rooms.....you are expected to shower fully naked before going in - complete with diagrams as to where you should soap! 
Coffee shops are a real institution in Reykjavik - can remember the name of the one on the main street up to the cathedral but it's on a corner and slightly lower than street level.
You'll need to get the bus from the airport to Reykjavik but you can buy tickets at the airport.
Depending on your flight times, you can go to the Blue Lagoon on the way there or back - they'll look after your luggage. All the tour operators offer that option (see Reykjavik Excursions above).
Blue Lagoon as an extravagance compared to the public baths but still worth it. I booked a floating massage which was lovely, but dh made do with plastering the silica sand over his face - which did indeed make your skin feel lovely. Your hair will feel like straw afterwards though
fine after a few washes
Because they are effectively on Double Sumner Time, you don't feel as if it is as dark as long as it really is, as what daylight hours there are are in the afternoon.