I can’t say for sure if the quest is still doable anymore, but here is a copy of the information from the LF1 walkthrough covering this quest:
Side Quest 43- Convince Magdalena (Q163)
76. Go to the undead guild again via Wendalas old place and use the Magdalena shrine map. Put Random, Sarah, Wendala, and Herbert. Use the beauty potion found in the mage guild on Wendala. Put some gold in the pot at the top and Magdalena will appear. (I had to put in 10000 to get it to work). Talk to her and quest complete. Before you leave, check behind the rightmost waterfall for a crystal rain. Talk to Vaartzis again about the Magdalena quest and he will give you 1500 gold and Wendala gets 5HP. Now go and visit Baretta as she has new stock in again. She sells 9x XP egg. After you buy one, she may then offer to sell you baretta's card of power.
----------------------------
Presumably the steps involved would stay the same if it
were still possible to do this quest. The 10,000 gold may be the most relevant piece of information there. I imagine the party composition would have to be different though. I'm not even sure why it recommends those specific characters, but I think Wendala might be required at the very least.