Lucky me,

My battery died and I had to get it jump started. When I got to the parts store, good news, the battery was under warranty.

Bad news, their diagnostic machine showed an open diode in the alternator.

Their solution is to replace the alternator. I'm curious as to whether I could just replace the diode pack?

Suggestions, please.

I always rebuild my alternators--it's fun and easy. I recommend you do the same, after buying the necessary parts online. Here's the procedure for rebuilding a common Ford 4G alternator (other models are similar):

https://www.askmehelpdesk.com/cars-trucks/faq-how-troubleshoot-repair-maintain-hondas-selected-other-vehicles-46563-13.html#post2518522

You will be able to buy a replacement rectifier. The challenge will be to get away with just replacing the bad diode.

I would think you could get away with replacing the diode pack but that may not be the only problem. Good luck with it though. By the way how does the van run for you?