RE: Exporting to Excel from MS GP
SSRS is definitely the way to got to create an Aging Report for AR.. And you don't have to re-invent the wheel, as others have been going thru this too:
community.dynamics.com/.../gp-ar-aging-report
BTW, just because Microsoft's brand is affixed on both Dynamics GP & Excel doesn't mean that they are working smoothly together, as they were coming from two complete different worlds originally and only got to work together easily about 10 years ago when Microsoft started providing out-of-the-box Excel reports to deploy with GP (about 150+ reports).
The OoB reports have direct data connections to the GP database, which means you can pull data live from the SQL server without even opening GP.. Unfortunately, building an Aging Report is a little more complex and requires stored procedures, which aren't necessarily easy to put in action within Excel.
PS: the Aged TB report in SSRS can be run with or without details about invoices and documents.