Chimney Repair

Got an estimate from a chimney repair company. After I looked it over I looked at the chimney to see what they were going to do. Well, overcharging and under working would be about what they were going to do. They even had some things on there that I didn't even ask for. The benefit was that I learned a few things, mostly that I can order the things I need online and do it myself but I have a few questions.

1. To install a chase cover do I need to take off the cement crown/cap that is already on top? I assume I would as the cover would not sit right on the sloped cement.

2. On the estimate they listed waterproofing the entire chimney. I looked up the stuff to do it.. Chimney Saver, $250 for 5 gallons. The house is 60 years old and it's never been done and there are only a few loose mortar joints that I can repair myself. Is the waterproofing really necessary?

3. I'm going to put a chimney pot on top. I assume the portion of the flue protruding will fit inside the pot given that the pot is taller than the flue and the inside diameter of the pot is more than the outside diameter of the flue. Regardless, how do you secure the pot to the top?

4. On the estimate there was listed a drop in damper. Is that necessary? I've never had any trouble with bats or birds getting in the flue ......... or is that for rain? But then if it's a drop in damper where would the water go???

Any advice much appreciated