07 sierra - won't come out of 4x4

I bought a 2007 GMC Sierra in December from a GM dealer, got a really good price and am very happy with the truck. It has the electronic 4x4 switch in the dash, I wasn't too keen on a non mechanical shifter but had not heard too many horror stories about the electronic shift on the newer models. Last friday, I put a friends boat in the water and shifted into 4 wheel drive to make sure I would not skid when pulling the trailer out of the water. Found it a little strange that it was hesitating going into 4 wheel drive but did not think much about that since it did shift. After pulling the boat trailer out, I tried to put it back in 2 wheel drive but it would not go. Tried playing with the switch and driving forward and back with no success. I remembered the old mechanical shifters where you had to drive back 15 or so feet to unlock the front hubs. So I went to the dealer where I bought the truck and the service manager did the same I did, played with the switch and went forward and back until it finally did shift back to 2 wheel drive. He said it sounds like a solenoid was acting up. Is this something I should worry about, they are going to fix it for me under warranty, but the truck only has 64,000 km on it. What will happen in a few years when the truck has a lot of miles on it and is out of warranty? Is this something I will be able to repair myself?

Thanks for any help!