Welcome! You will get all kinds of advice, suggestions and experiences with your questions. It is good to think ahead and look for the pratfalls; for that I applaud you.
I know of lots of people with greys (and other dogs, for that matter) who are gone for 10 hours a day and the dog is alone. A potty break mid day is good. I have a dog door, which won't work for you, but it allows me to work all day and still have them comfortable.
Lots of others live in apartments/condos with their dogs, too.
We go to the park once a week (just got back, actually), but it is for greyhound playgroup. All hounds, all muzzled. We are diligent with our hounds and haven't had a major incident. My dogs have gotten their skin tears in my backyard!
I am also sorry for the loss of your lab. It is like losing a limb.
Good luck with whatever you decide!