Based on what you’re telling me, if this only happens in 2nd gear then that synchro is shot. If you can’t strong arm it into gear with clutch to the floor or it grinds if you do then a portion of the transmission needs to be rebuilt. I wouldn’t take anything less than a brand new transmission and neither should you. I would not trust a dealer to rebuild it, it’s too complex and that is not a forte of any dealership service department.
Based on what others on the forum have experienced, It will take at least a month or more to get a new transmission approved and installed. You should get a loaner right away, I wouldn’t take no for an answer.