Hello dayv,

your available replacement motor is an old 1FK7 generation 1 version. Additionally a different encoder type is used. The remaining motor features are compatible.

This means for a replacement, that the rated data fits. 
But a new motor commisioning is necessary, as the electric data is different.

Concerning the encoder you will have more effort:
The faulty motor has a DRIVE-CLiQ resolver with 15bit (R15DQ). So the signal cable is a DRIVE CLiQ cable.
The replacement motor has an absolute encoder without DRIVE-CLiQ interface (AM2048S/R). This  has to be considered in the drive configuration and you need a different signal cable and in addition the Sensor Module e.g. SMC20 for evaluating the encoder data.

Mechanically the motors can be replaced without any changes. (Concerning shaft and flange)
To be sure about the overall length and so on, I'd recommend to compare the dimension sheets. For the generation 1 motor you can use CAD-Creator, for the generation 2 motor you can use DT-Configurator DT-Configurator.