I am a complete newbie to Apex triggers, but have semi-successfully completed a trigger that will initiate from an opportunity.  The trigger is supposed to retrieve the associated contact Ids by retrieving them from the OpportunityContactRole.  Once the contact(s) have been identified, I want to send an email to the contact and update a field within the contact. 

I have three main concerns/problems:

1. If there is more than one contact associated to an opportunity, only one contact is updated and sent an email
2. Is there a way to limit emails to send only once, rather than every time an opportunity is edited and meets the criteria? Or will I have to upsert an opportunity field (i.e. - a checkbox indicating email sent) and make sure that if that field is checked, the trigger does not fire?
3. Is this trigger "bulkified"?

I have copied the applicable code for my trigger in progress below.  Again, my main issue is when there is more than one contact associated to an opportunity:

trigger portalEmailSend on Opportunity (after update) {
for(Opportunity oppEmail : Trigger.new) {
        if(oppEmail.StageName == 'Qualified' && oppEmail.Account_Name_Copy__c == 'Something'           && oppEmail.Send_Auto_Discovery_Portal_Emails__c==True) {       
            List<OpportunityContactRole> theOppConRole = [SELECT Id, OpportunityId, 
            ContactId FROM OpportunityContactRole WHERE OpportunityId=:oppEmail.ID]; 
               //get OpportunityContactRole ID from Opportunity that initiated trigger
              for (OpportunityContactRole contactRole:theOppConRole) {
                 // add OpportunityContactRole to the main OpportunityContactRole list
                 theOppConRole.add(contactRole);
                     
                 if(contactRole.ContactId==NULL){

                 }    
                 else{       
                 //Sending email to matching contact(s)
                 Messaging.SingleEmailMessage mail = new Messaging.SingleEmailMessage();
                 mail.settargetObjectId(contactRole.ContactId);
                 mail.settemplateId('IdofTemplate');
                 mail.setsaveAsActivity(true);
                 mail.setsenderDisplayName(oppEmail.Owner.Name);
                 mail.setreplyTo(oppEmail.Owner.Email);
                 Messaging.sendEmail(new Messaging.SingleEmailMessage[] { mail });
                
            
                //updating opportunity stage field in matching contact record(s)
                List<Contact> inQuestion = [SELECT Id, FirstName, LastName, 
                Opportunity_Stage__c FROM Contact WHERE Id=:contactRole.ContactId];
                    for (Contact contactMatch:inQuestion) {
                    
                    contactMatch.Opportunity_Stage__c = 'Qualified';
                    inQuestion.add(contactMatch);
                    upsert contactMatch;
                    break; //exit after upsert to avoid continuous looping
                    }
                    break; //break initial for loop that processes contact data
              }
            }
        }