New pool owner

Hello all! My significant other bought a house with a pool in October, and I've used this forum to learn a bit about the maintenance and certain procedures. It has been a useful tool thus far.

We're located in the DC area and got to use the pool for most of October, but ended up closing it due to the amount of leaves falling in. We used the previous owners' pool service for the last few weeks of cl eaning and the closing, however I do not want to use him again due to his exorbitant rates ($600 to close the pool) and a comment he made about always adding chlorine, even if there was already too much chlorine in the pool. He just seemed to be too laissez-faire about the pool and equipment for my taste.

About the pool: from what I have gathered, it's somewhere between 22,000-26,000 gallons with a small-ish attached spa, and it was built by Anthony pools any time between 1970 and 1988. It was replastered a couple years ago. The equipment that is there now is a 1hp Pentair whisperflo, a 3/4hp Polaris pump, a 60sq. ft. FNS Plus DE filter, and a Purex Triton 350M minimax (millivolt). The heater is from 1993, and the other equipment looks about the same age. Updating the equipment is what brings me to this forum. Hopefully I can find the answers and advice I'm looking for!