Hello. What fatal crashes have you encountered, exactly? Because that seems weird...
Also, nothing you've described is a bug. The bodyparts are meant to be placed by literally getting close to the body and placing them, no interaction is needed.
You are not able to open the menu or bring up the gun because that would bug it. You just need to place the bodypart and you're good.
Hope you give it another try, I'm sorry the experience was dissapointing to you!
God bless.