Hi, I am also having a lot of problems with this LTW and think it's glitched. I have had my Sim marry a RICH, as labeled by the game, sim. The spouse drowned in the pool -- no cheats, no walls. However, when the spouse returned as a ghost, the gold digger saw him, had a conversation with him, but still no fulfillment of the wish. They even cuddled on the bed together and kissed!
I ended up trying again with a new spouse, but the same thing happened.
I believe the problem is that the dead spouse returns as a fiance instead of spouse. The game then doesn't register the ghost as the dead spouse so it can't complete the wish. I believe in the original base game, the dead spouse came back as spouses, which lead to remarriage glitches, but the wish could be completed. They need a new status: deceased spouse.
Also, the gold digger can't remarry the dead spouse because they option to marry never comes up. They are stuck as permanent fiances.
Has anyone completed this LTW successfully recently? If not, would someone try to test it out? It doesn't take much time. In fact, the guide on this site is very good; it's just the final seeing the ghost part that is not working.