For the reputable dealers, consider checking the Better Business Bureau before you buy anything. bbb.org. They have compiled reviews of many businesses, responses, complaints, and known issues. This is a great place to start and I have had many good experiences using the BBB.
Second, the gold standard is buying a Panerai through an authorized dealer. I know you are trying to save some cash. So did I (i have two pam's, both bought on the gray market). If I could take it back, i would, just for the peace of mind. If the model you want is contemporary, and the base and marinas are, your best bet is seriously through an AD. It's tough too -- there aren't too any AD's around. Tourneau is a very common AD for panerai although they get a bad rep from many watch enthusiasts. It depends on the model you want. if you are after a discontinued model or rare model, you may have to go through gray market. First, you need to decide exactly which model you want and what you are willing to pay, so start there.
I really am putting in a strong vote for an AD. I understand there aren't any AD's that are near Alberta. The closest ones I'm seeing are like... toronto? ontario? That's far. You are well off having some patience, doing some searches, and saving your purchase for when you're on your next trip (if ever).
Third, you are not nuts one way or another in terms of your trade. It depends on the condition of your Submariner, the model of the Panerai, and what you are needing to sure up the deal. Decide which watch speaks to you the most. This is about personal preference. I have Rolex's and Panerai's and sometimes I still can't decide which I prefer more.
I don't know any online dealers that are reputable, to be honest. I had a better-than-lukewarm experience with essential-watches.com. I had a semi-crappy experience with interwatches.com.
The other problem is you don't know where your watch has been. You don't know how many owners, if it's been modified, etc. These companies somehow seem to get their hands on new or used or pre-owned watches and have their internal watchmakers polish up the cases to make it seem LNIB. The biggest fear of course is getting a counterfeit -- and some of the counterfeits out there are very convincing.
Good luck, hope you find what you're looking for. And please keep us updated! And post pics!