And what criteria will you use to find the correct record?
Some examples of Scripted Finds: Scripted Find Examples
And where will the data come from to update the record? What data will that be?
A script can use set field to modify the value of a field, but what you would put in the "calculated result" parameter of this script step has not been specified by you.
"Get the record" may have meaning in the context of PHP (I have no experience with that method of custom web publishing), but it is meaningless in the context of just FileMaker. Once you find the record, you already have a found set of just that record and it is the current record. Nothing else would be done to "get" a record.