In a former life (in a galaxy far, far away) I consulted on AS/400 ERP software, including JD Edwards. I have done a few conversions from AS/400 files to Sage 100, but it has been awhile. Anyone looking at these types of conversions now is probably using the legacy versions on the AS/400.
I also have another consultant here in LA who is a technical expert and programmer for AS/400 OS and file structures, so when it gets too much for me, I call on him. Based on what I do now (which is not too technical), I would readily call on him.
The file structures for these systems are not compatible with PC systems in their native form, but there are built-in utilities to convert down to ASCII formats. Either that or printing to text files and downloading, which is necessary when they do not have the latest Windows integration when using PC's as terminals. Most of the time it takes less time to have them license the appropriate software to download data files seamlessly to a PC.
Oh, yes, I have experience.