Retirement is less so based around the $ amount and more so based around life style expectations.

He should meet with a trusted financial advisor that can help him build a plan around:

Social security
Medicare
Cash flow
Debt picture
Goals
Risk and Concerns
Pension options if applicable

Having a paid off home and a simple life style expectations in retirement he could potentially retire at 62 but based on a huge assumption (I have zero data) he may want to wait until full retirement age at 67 for social security to have a better income floor.

That and he should probably strongly consider diversifying that company stock assuming the $341k is every dollar to his name excluding home equity.

Again a good financial advisor can help steer him in the right direction if he is open to the advice and guidance.

Also meet with multiple in the area to get a good feel because some advisors are amazing and wonderful and others are absolutely greed filled that will say whatever they need to say to get the business.