Each situation is unique. I recommend you run through the IRS How Do I File a Deceased Person program. It is very detailed and will tell you exactly what is best for your situation.
If for some reason you did not receive your stimulus, you can have it added to your refund. The IRS does not begin accepting returns until February 12 so all stimulus should have been received by then. See How do I claim the Recovery Rebate Credit?
I am very sorry for your loss.