It is likely that a new servo driver and motor can easily be substituted.
For ballpark, a 750W modern brushless AC servo is about 700€ in the EU, all-included with 22% VAT.
These have both step/dir and 0-10V analog inputs, and should plug in into most-anything industrial.
The new servo is vastly better, but wont make much difference functionally as your controller typically will not be able to utilise the new servo to it´s full capacity.
Tuning the new servo may be easy or hard, depending on your controller and documentation, and sometimes on the servo.
Setting "safe" parameters on the servo is likely to get you excellent results, but much less than a new modern servo could ideally do (with a new controller).
Fiddling with the new servo is likely to take about a week of work, unless a tech familiar with the old machine can be located for advice, cutting the fiddling by 80%.
You can do 90%+ of the fiddling, with 10% of advice online.