Here is a chicken pasta dish that I make in the summer. I make my own pesto and I grill the chicken breasts but since you are a novice, I don't see why you couldn't buy a rotisserie chicken and already prepared pesto at the store.
Pesto Chicken with Bow Ties
2 large chicken breasts grilled (use a rotisserrie bird if you like)
1 cup pesto (homemade or store bought)
8 oz bow tie pasta, cooked and drained
1/4 c parm cheese, shredded
8 oz package of sliced mushrooms
2 T butter
Cook the pasta according to the package instructions. Meanwhile, in a medium sized saucepan, cook the mushrooms in the butter over medium heat until they are soft (about 10 minutes).
Cut the chicken into bite sized bits. When the pasta is done, drain it well and toss it with the fresh pesto (can use store bought), the mushrooms and parm cheese.
Note - I sometimes throw in a handful of homegrown chopped tomatoes, in with the pasta at the end.
This is great with a tossed salad.
For a romantic dessert, I would either purchase or make something chocolate.
Good luck with your dinner - I know your girlfriend will appreciate the effort! I've been married 3 years and my husband cooked dinner ONCE. He made tacos one night when I worked late and when I came home and saw him standing over the stove - I grabbed our camera and took his picture because I knew it would never happen again!
Let us know how things turn out.