Thats a 984 compact, there is no such things as Quantum compact.
I'm afraid that I don't have much in the way of good news.
Workshop32 for Modicon isn't too bad to use, but IME its prone to blue screen. Despite that it a little better than Proxworx32 which is notoriously buggy and slow and seems to suffer from an attention deficit disorder, sometimes it just hangs for a minute and then suddenly remembers that it is supposed to be doing something, usually at the worst possible time.
Proworx NXT is the WIN95 programming software and if you can get your hands on it then thats your best choice. NXT was easy to use and I never had bug problems with it, I just could not get it to run under WinXP. Right now there is no good software solution on the market for the 984 family PLCs.
More bad news: You can't import your program into Workshop32 from NXT. What you can do is connect Workshop32 to the PLC and read the program out. Then if you have NXT you can export the comment database and then import that into Workshop32. Been there, done that. Several forum users have NXT or Prowrox32 so one of us might be able to assist with the documentation export.
Unless your customer already has a good MRO inventory of spare parts for that POS then you may want to suggest he either start keeping an eye on E-BAY for chances to stock up on spare parts or begin considering a replacement. That PLC has been out of production for nearly a decade.