Totally normal.
I had the same feelings and my first two are two and a half years apart.
I showed him lots of pictures of babies and kept reminding him that there was a baby in my tummy. I used newborn diapers on one of his stuffed animals so that he would get used to seeing baby things around the house. I took him shopping with me to buy the baby a gift, etc. I basically spoke to him every day about it.
And the day after we brought my daughter home, he drew all over her soft little head with a ball point pen. It was scary and funny all at the same time.
I also did the same thing with my daughter, who turned two nine days after my second son was born. We were really worried about her because she was such a Mama's girl, but everything turned out alright. She's actually turned into quite a nurturer.
So just relax. Enjoy your second baby and have fun with all of the little obstacles that may seem huge right now, but will dwindle with time.