I'm not at all sure that a full OpenGL tutorial is necessary, but that's not to say it would hurt.
3D modellers are just as hard to find as 2D spriters, to be honest, (I've hired games artists in the past) but yet loading and handling 3D objects created in random formats is more difficult than someone sending you an RGBA PNG and editing as required to make it fit. I've made sprites for my game in Blender, for instance, by importing 3D models onto an isometric perspective and exporting them as PNG. It's not at all difficult compared to loading and rendering massive amounts of OpenGL TRIANGLE_STRIPS, taking account of CCW-windings, backfaces, loading from a 3D file format (*is* there a standardised one for 3D models?), applying texturing, modifying camera positions and lighting etc. and in fact some of those stages have exactly the same problems as you'd face in trying to create 2D isometric tiles but much more so. Hell, getting a model and texture from an artist and getting it to the point you can slap it into the game at the right scale is a heck of a lot of work compared to giving them an RGBA PNG template and then loading the result when you get it back (one call to a "load_png" routine and one call to draw it at the right point which is a two-line formula).
The difference is, I can knock up an RGBA PNG on a template background and stick it in the program. I can get iso graphics from the Internet and just throw them in with a simple resize or crop. It won't look great but it will work and I can literally sit in MSPaint or equivalent and touch them up to make them perfect. But knocking up "any old 3D model" for that kind of use is something I consider beyond my skill (I can JUST about knock up an isometric 2D PNG from a 3D model in Blender format if I follow a tutorial I found online and don't touch any option in that program except the ones I need).
There's also the performance issues to consider - do you want to be optimising your 3D model loading routines, camera rotations, etc. when you're new to programming in OpenGL and just want to see something on the screen? And, using OpenGL, rendering 2D is easier than rendering a 3D model using the same commands (hell, the windings, triangle strips, vertex arrays etc. necessary to render one 3D model can get horrendous, combined with external file formats). "True" 3D has a lot of advantages but most of them are quite minor and most people are willing to sacrifice them - e.g. you can view from ANY angle including 0.1 degrees off center so you can rotate "smoothly". But most games of that genre don't let you rotate because they've assumed it will be from a fixed angle. Once you have that kind of 3D "anything, any angle, any where" setup, the isometric viewpoint loses its appeals because of things going behind other objects (e.g. in Bastion, it's 3D accelerated but it's basically 2D projection and they have to "fade" the graphics that you have walked behind - but there are reasons the programmers took that trade-off instead of having a full-3D environment). Literally, by that point, turning your game into an FPS or a side-scroller or an iso or anything else is just tweaking the camera in 3D. That might sounds good but it also shows the complexity of what you're doing programmatically and just how much data you have to create just to throw it away because it's on a creatures backside and will never be visible.
If you do go OpenGL, I can thoroughly recommend the OpenGL Superbible, but the 5th edition focuses only on shader-style drawing which I find obtuse and unnecessary for a simple game. If you can get a copy of the 4th edition, that's almost the perfect introduction to "direct rendering", "vertex arrays" and the newer "shader model" styles of drawing in OpenGL. But, personally, I'd experiment with a 2D game first, get up to speed and if you find it's too tricky the move to 3D is required anyway. And if the game hits performance problems, you can shift to 3D acceleration and ease yourself in. My philosophy is: the game is not the graphics, it's still a learning experience, and I can knock up the graphics in MSPaint if necessary but I can't do 3D modelling myself and wouldn't like to try.