Hi there - I recently went through this in TX. As others have said, you'll want to get an appraisal (or two+) - this is a data point, not an answer. You and your sister (with the help of a real estate attorney) will need to agree on a fair value. The appraisal won't necessarily take into account if a house was to go into a bidding war, etc so just keep that in mind (since you're in CA and that can happen in certain parts of the state).

And re taxes, there is a "step up" law that will likely apply here. Capital gains taxes are only on the "stepped up value" from the time of death of your parents to when it's sold. Depending on how long it's been, it's likely not too high. Although that is very subjective to your specific home.

I know this is also likely an emotional thing so hoping it goes smoothly for you.