Ours is one year newer than the OPs Journey. It's an '04 Itasca Horizon 36 GD and is toating the C-7 330 HP CAT and, the Allison MH 3000 transmission. It too has only "ONE" fuel filter, very visible from the rear of the coach. But, the BUILD DATE is very important here. The bean counters at Freightliner went head to head with the CAT folks around that time and they won. The got the right to put only one filter for a shore while. Then, even in the same model year, they went back to two fuel filters.
And, as has been stated, if there's a secondary filter, it's on the passenger side of the engine, up high, and may or, may not have a hand priming knob right on top of the filter housing. But, you'll have to do one of two things to see if you have that filter or not. One, pull the bed apart and see for your self or, do as has been suggested and call Freightliner and see what they have to say. Just have the last 6 numbers of your Vin ready when you call.
2004 ITASCA HORIZON 36GD, 2011 GMC Sierra 1500 4x4 Toad '08 GL 1800 Gold Wing
Retired-29.5 yrs, SDFD, Ham - KI6OND
Me, Karla and the Sophie character, (mini Schnauzer)