1992 Honda Accord Replacing ball bearings in front suspensio

Suspension problem
1992 Honda Accord Engine Size unknown Front Wheel Drive Manual 250000 miles

Hello, We've been noticing a crunching/grinding noise for sometime that recently went from intermittent to constant. The mechanic says the ball bearings on both sides of the front are shot and need to be replaced. We have a couple of questions about the recommendation:
1. How urgent is this repair? Ie, will the wheel fall off the car?
2. He said the left side is worse than the right, though the right is definitely louder and has been going on longer. Possible?
3. He said this will cost ~$400 for both. Does that sound right?

Ultimately, we come up to the question of whether it is worth it to make this repair on a car that may or may not be worth $600 resale. But thats a whole other kettle of fish!

Thank you for any responses.