welcome from NJ and yes its very do-able , I had a space between cabinets that was designed for a portable toliet but it would sit right next to a bed so i said no way and i built a really nice large cabinet that fills the space. I suggest measuring the space, then drawing it out on paper, then you can construct the cabinet out of corrigated cardboard, the stuff they use for commercial cartons. Then you can take the model cabinet inside camper and do a dry run with it , does it fit ? do i like the shape, the look ect. if that all works well. then you can construct the cabinet. I recomment using ferring strips to  creat the frame. This will keep the weight down( your high wall must be pushing big lbs allready) and help keep more space inside. i used a very thin finished 1/4" ply board  for the shelf sturdy enouh but light weight, and then i used finished 1/2" plywood for the top and front. I had to go heavy here because my kids might sit on counter or kick door front by accident. You can go as simple as i did or can get fancy and add draw slides and rollers etc. and then finish the cabinet with stain or paint to match your interior. I had all the hardwear in my shop at home ( the hinges and the door pull) so saved a few bucks there. you can see some pics here of the space before i put the cabinet there and how i used to put a ruber tote bin there to put stuff in. I use this new cabinet for all of our plates cups silverware paper goods and cooking accessories. and the extra counter space is precious since my kids always want places to put stuff durring our trips . the pictures are before the wood was stained. buidling the cabinet out of cardboard first added more time to the mod but it really helpped me adjust the size and loaction before i started cutting and building out of my actual materials and saved me time and money in the long run.
pics
https://www.flickr.com/photos/.....res/oLsJtF