Hey Jason,
Awesome, the hard part is over then :-)
Since you are using the Record ID# I would recommend using "&rid" instead of "&key". Its a subtle difference, but its important. However, when adding a record the "&rid" and "&key" parameters are unnecessary (since a key value has not been assigned yet). Below are examples on how to setup an Edit Record and an Add Record function.
/* Edit an existing record */
function showPosition(position){
var editURL = "bnifp6kni";
editURL += "?a=API_EditRecord&rid=" + QBU_recid;
editURL += "&_fid_13=" + position.coords.latitude;
editURL += "&_fid_14=" + position.coords.longitude;
editURL += "&apptoken=YOUR_TOKEN_HERE";
$.ajax({url: editURL,async:false});
location.reload(true);
}
/* Add a new record */
function showPosition(position){
var addURL = "bnifp6kni";
addURL+= "?a=API_AddRecord";
addURL += "&_fid_13=" + position.coords.latitude;
addURL += "&_fid_14=" + position.coords.longitude;
addURL += "&apptoken=YOUR_TOKEN_HERE";
$.ajax({url: addURL,async:false});
location.reload(true);
}