Steve,
It's hard to really answer the topic here without seeing the bike, but I can say for sure, the 05 SEEG seat has the all time most uncomfortable seat H-D ever made. The stock seat's gotta go for sure. Engine wise, I don't know what it's got for mods, but if it's bone stock, changing the intake, exhaust and tuner is well worth the money in performance gained and smiles per mile. Once that's completed, I think you'll find you'll be quite happy with the 103 and the 5-speed trans. I see no reason to spend the money to swap out the trans on this to a 6-speed. Suspension is a personal thing. You might be very happy with the stock air shocks on the rear and the front end the way it is although coming off the Magnum, I have to believe you're going to spend some time getting used to the " Harley Ride " Progressive fork springs help a lot and cost a fraction of what the Traxion Dynamics front end change out costs so that bears looking into if you want to stiffen up your front end some. That's it from me. The beauty in owning a Harley-Davidson is in making it your own. Changing this here, that there till it doesn't look like someone else's and has a personal feel to it. You've bought one of if not the best model CVO bagger ever made, so you're most of the way home already.
B B