How do I contact Heartland to also inform them that I'm having this repair done?
If your dealer is repairing your unit under the HL warranty process and will be reimbursed by HL for the repair, then HL is more than likely aware of the repairs. As I understand the warranty process, the dealer contacts HL for authorization to complete the repair and HL agrees to compensate dealer for said costs before the work is completed.
No need to contact HL if the dealer is responding favorably to your needs and the issue is being resolved to your satisfaction by the dealer.
Here is a good thread on the Heartland Warranty Process that may add additional information.
Hope this helps.
Brian