I heard that it's possible to go through DOH Immigration in Al Mourjan. Is this correct?

I'm trying to figure out some logistics. I had posted above - friend & I are traveling PHL-DOH and then DOH-MEL, two separate tickets, so we have to pick up & recheck our luggage in DOH. We have a 10 hr layover in DOH. I was thinking about doing Discover Doha transit tour as well, but no clue how the logistics would work, so perhaps this is two separate questions:

1. If I go through Immigration in AM (how?) then do I just walk through the immigration line and show some sort of paper to go get my luggage and recheck it?
2. Once I've re-checked my luggage, I assume I go back through immigration/TSA and then go to the tour desk, and then I'd have to go back out again through Immigration/customs.

Or do I go to the tour desk first, and perhaps they would do the immigration/customs thing, and from there get luggage, recheck, and wait somewhere outside the secure area for tour pickup?

Sorry if this is a bit unclear/confused. TIA