If you want the best and most unbiased opinion you should contact a NACHI approved home inspection service. They will come out and provide you with a written report on the counters, and anything else you may have concerns about.
They will remain completely neutral and have plenty of experience. Most are former contractors and builders with over 20 years in the trades.
If you would like me to see who the nearest inspection company is please provide your zip code.
Yes, the process is labor intensive if the surface is rough. Yours just needs a little more honing and a polishing. Maybe just a polishing will do.
If the company that comes out to do the repair doesnt have at least a dozen or so diffrent grinding disks, and doesnt make a big mess in your kitchen then they are not worth their salt.
Granite finishing is a progressive process. You start with a heavy grit and work down to a grit that would probably polish out a scratch on your smart phone screen.
All in all it shouldnt take more than a day if that to do the job.
I did a resurfacing for a Lady about a year and a half ago. As a novice it took me two days to get her counters shinning like a drill seargents jump boots.