Finish Feedapi based aggregator | Private Company

Small, quick project. I need assistance creating a feed aggregator using feedapi and mapper. My xml file is not rss, which it can be, but I need validation to my schema.

Items to complete (this is my best guess being a noobie -- fill in the missing pieces as you are the expert):
1. Custom xml parser with validation
2. Mapping of elements to content type (content-type already created)
3. I think the instructions say to use drush feedapi for the cron job -- setup
4. When a feed is refreshed, I need it to 1) add new items/nodes, 2) update items/nodes 3) delete nodes that no longer exist in the feed xml file.

I've posted this in forum under paid services on drupal.org as well.