This is my first time doing an engine replacment

i currently have 99 percent off electronics plugged into new engine n new hoses attached, I removed the old axles and now that my transmission doesn’t have it front drivetrain. will I need to cover up the whole on transmission so fluid doesn’t leak when I fill it back up?
also now that it has no front axles n it wa originally a rwd car could I just upgrade my rear drivetrain and maybe weld diff if needed and it will be fully rwd or did I just waste a lot of time? I thought I bought a g37x 2009 motor thinking it was the same one awd and all but they were selling 370z engines not specifically saying it’s rwd

 

The VQ37VHR engines are all the same across multiple cars rwd and awd.
The only difference between awd and rwd engines is the upper oil pan. The awd oil pan has the accommodation for the CV axles while the rwd don't.
The upper oil pan are interchangeable.