Thank you all for the feedback and suggestions. After reading all of these I'm agreeing with the idea of moving forward, working and living on what I have already saved up (which includes the "checking account" inheritance) and not counting on the larger inheritance. I am going to looking that FireCalc someone mentioned. I'm still pondering the idea of some level of withdrawals in order to pursue some other work situation (less hours worked - more time on things I enjoy)
My parents have been giving the kids distributions the past few years, which I've regularly maxed out my Roth IRA and HSA. I have a pretty good handle on investing and saving money, and am always running calculations on how much money will last how long.
Two more things. We will not be charging my mom rent for living in our condo.
And I have a new worry, now that someone mentioned my mom remarrying some guy, that could inherit the money? This opens up a whole new question about powers of attorney, etc, when a parent reaches later stages of life and may make some questionable decisions, etc. But that's for another thread.
Also, I don't think we will be liquidating any stock as the tax liability would be massive. It's my understanding that when stocks are inherited, teh cost basis is adjusted to the current market value. I could be wrong.