"I just used the wrong word for it. It took a very very long time to process, not very long to download after it processed"
As I suspected.
"And on a related note, once I modified the tree as requested, I couldn't export a GED from FTM. It just kept saying there was some sort of error."
Do you really mean FTM, Family Tree Maker the PC program, or do you mean you made changes to the online tree (Ancestry Member Tree or AMT) and then couldn't export a GED from the modified online tree?
I suspect you meant the later and if that's the case try making another change to the online tree and try the export again. If it still fails note the error message and contact Ancestry support.