What size Mojo did you get? The link in your first post is for the .40 size Mojo.
If this is the case a removable a removable wing is not needed unless you have a micro car for transport. Extra weight is your worst enemy.
There is nothing complicated about attaching the wings to the fuselage. Check out the thread "Mojos for Dummies" in the ProBro forum.
The aileron mod (cutting the outside corners of the ailerons) is a good idea. It may save you a small rebuild if your wing hits the ground.
For the .40 size Mojo the most popular engines are .72-.82 four-strokes or .50-.55 two-stroke engines, but a .46 two-stroke will suffice if your Mojo is not too heavy.