The granite counters were sealed with a water based sealant with 2-3 coats in the appropriate recommended manner per manufacturers instructions.

I would also look for popped nails, and and exposed nails on penetrations, where the sealant is gone away.

Depending on what kind of sealant you already have in place makes a difference, but last time I looked Walmart ( or any big box store) had  both black jack ( I LOVE THAT STUFF EVEN IF IT IS A COMPLETE MESS) or the white elastic stuff in 5 gallon buckets for like 75.00 to 100.00.

Should I put some sealant(I think that's what it's called) on the crack.

Something like this:   http://www.amazon.com/gp/product/B002RT7BH2/They also have similar items at lowes/home depot.As far as the sealant on the tub/shower...why was that installed?  

My contractor tells me the sealant is very expensive.

Perhaps some stain/sealant is better than nothing. 

the sink is stainless steal that would just need a little water sealant around the edges. 

Use non pourous tile and rather dark grout or any grout with a good sealant on top to make cleaning the grease easy.

If you do anything with the drive, scrub it and treat or stain it (if concrete) or roll a sealant coat on it (if asphalt).