nuts are good for you, but they are also high calorie. a serving is an ounce or 1/4 cup, which isn't a lot of food. same for the avocado, it's got all sorts of good stuff for you in it, but a serving is 1/4 of an avocado and your fat is going to go through the roof if you have a whole one. but as with everything else, when you eat multiple servings of things at a time, the calories add up. and that's true whether it's nuts, avocado, chicken or chocolate cake.
nuts to replace chips is a bad substitution idea imo. chips are volume food and nuts are the opposite. if you want to replace a volume/munching food, something like air popped popcorn or vegetables that can be sliced into sticks and perhaps dipped in a yogurt or hummus based dip are going to get you more bang for your calorie buck. a few nuts might round out that snack, but it should not be the basis of it.
-google first. ask questions later.