How can I increase the length of First & Last name attributes from 32 to 50 in Contact Record in NetSuite.

No, you can’t customize standard fields in NetSuite other than changing the field level help, label, or how they display on the form.  You could create custom fields and then hide the existing ones (you would need to monkey with any standard reporting, and might need to fill these in on the backend depending on what you’re doing with contacts in the rest of NetSuite).  You could also create your own custom record with all custom fields if you really don’t like standard NetSuite, but that’s probably overkill if this is your only issue.