Saw a similar issue, but not quite the same, so here goes.  We have a bunch of custom web forms feeding leads into SF.  We worked with a developer to make these.  Not quite straightforward as they not only include standard "Name", "Email" and "Message" fields, but also take a WooCommerce shopping cart and dump the contents into a custom SF field.

The developer we worked with went as far as getting those forms into SF as leads.  But there is no checking to see if a contact with the same email address already exists. Here's what I'd like to be able to do:

1. A lead comes into SF from our website and is assigned by default to our Sales Manager (this happens now)
2. SF checks to see if that email address already exists as a Contact's email address
3. If it finds a match, it changes the Lead Owner to match the Contact owner and sends an email to that owner

We can take care of the duplicates when converting Lead to Opportunity.  Is there a way to do this? 

New to VF here...

I have a custom object named Materials__c.  It has a Master/Detail relationship with Opportunity, so any one Opportunity can have multiple Materials__c objects.  On my VF page, I can reference fields from Materials__c easily by using {!Materials__c.FieldName} because I'm using standardController="Materials__c".  Two questions:

1. How do I reference things on the Master object?  Like how do I reference Opportunity.Amount or Opportunity.Stage?
2. Taking it a step further, how do I reference fields from Objects the Master is related to? Like can I reference fields on the Account page of the Account that the Opportunity is tied to from a VF page that has a standarController of Materials__C?
 

Total Apex newbie here, but here is what i need.  Hopingn someone can point me in the right direction to start.
If I want to run an action on my Contact records all at once, what's the best way to make that happen? Specifics...
Each Contact record has a custom check box and a custom date field.
I want to be able to "tell" the system to find all records where the checkbox is checked, clear it out, and add today's date to the date field for those records. I want to be able to do that on an "on demand" basis, not a one time thing. 

Is that possible? And if so, where would I begin?