I created a custom button for the standard Opportunity object and it works fine when I put it on a standard page layout on the opportunity, but it's not working when trying to use it in my VF page. (Action doesn't perform and I get sent to a "URL no longer exists" page).

Button action is essentially to check / uncheck a custom checkbox field, "RFQ_Receipt_Sent__c".

Any help is appreciated, hopefully just a small fix?

Custom Button (Yes_Send) Code:

{!REQUIRESCRIPT("/soap/ajax/19.0/connection.js")} 
var v=new sforce.SObject("Opportunity");
v.RFQ_Receipt_Sent__c="{!Opportunity.RFQ_Receipt_Sent__c}";
v.id = "{!Opportunity.Id}";
v.RFQ_Receipt_Sent__c=="1"

if(v.RFQ_Receipt_Sent__c=="0")
{
v.RFQ_Receipt_Sent__c='1';
result=sforce.connection.update([v]);
alert("Success! The RFQ Receipt has been sent. Click OK to return to the opportunity");
}
else if(v.RFQ_Receipt_Sent__c=="1")
{

result=sforce.connection.update([v]);
alert("Oops! It looks like an RFQ Receipt has previously been sent, so we better not send another automatically. Click OK to return to the opportunity.");
}
window.location.reload();

Simple VF Page:

<apex:page standardcontroller="Opportunity" extensions="SendRFQReceiptControl" showHeader="true" sidebar="false">
 <apex:form >

    <apex:sectionHeader title="RFQ Receipt" subtitle="Would you like to send an RFQ Receipt to {!primcontact.Name}?"/>
     <apex:commandButton action="{!URLFOR($Action.Opportunity.Yes_Send)}" value="Yes Send Email Now"/>
      <apex:commandButton action="{!cancel}" value="No - Return to Opportunity"/>

 </apex:form>
</apex:page>

Controller (used to grab oppty's primary contact info)

public class SendRFQReceiptControl {
    public final Contact primContact {get; set;}
    public final Opportunity o {get; set;}
    public SendRFQReceiptControl(ApexPages.StandardController controller) {
        this.o=(Opportunity)controller.getrecord();
        try{
            ID primContactid = [select id,contactid from opportunitycontactrole where opportunityid=:o.id and isprimary=true LIMIT 1].contactid;
            primContact = [select id,name from contact where id=:primContactid limit 1];
        }catch(QueryException qe){
            system.debug('ERROR Querying contact:'+qe.getmessage());
        }
    }

}