Q.starting a garden
I would like to start a garden soon in my backyard, but before I do does the first layer of grass have to be removed before tilling? There is another place also that I want to plant alongside my fence. However, every year there is pampas grass that grows there. Will that have a negative affect on growing my tomato plant?

Congratulations on starting a new garden! It's fun to have a blank slate to get started.
Yes, I would most certainly recommend removing the sod prior to tilling the soil.
Have you considered gardening with raised beds? This is a wonderful way to garden and you would not need to remove sod.
As far as planting anything near the Pampas Grass, remember Pampas will continue to spread and grow. You may want to situate your garden away from the Pampas grass, or remove it entirely from you yard.
I have listed a few links for you to get you started.
Gardening Know How is an excellent source for information about all aspects of gardening.
Good Luck.
https://www.gardeningknowhow.com/edible/vegetables/vgen/starting-vegetable-gardens-guide.htm
https://www.gardeningknowhow.com/ornamental/foliage/pampas-grass/pampas-grass-removal.htm
https://www.gardeningknowhow.com/edible/vegetables/tomato/growing-tomatoes-guide.htm