My Journey is a bit older, but I also have the closet slide and limited access under the bed. To improve access, you can remove the mattress and the wood cover fairly easily, than you can remove the entire bed frame for even more. Than as others have mentioned, you can access from below, and I'll add that I've read where people have removed the radiator for the best access.
When I replaced my surge tank here recently, I found that there is an air dam above the radiator that you can remove easily for the most part and get excellent access to that tank...and other portions of the engine. I'm pretty sure that now that I've done it, I could do that job in 2 hours if necessary. But probably won't need to for another 77,000 miles.
Here's a link to the surge tank job:
Replace Surge Tank
