I found an old AD&D DMG from a starter set I had as a kid, and I'm porting it to 5e for a group of 4 level 3 players. This is the first time I've tried this (I never really played AD&D, just read the books).

I'm mostly going on Wizard's conversion guides; most of the monsters are pretty familiar, so I'm just creating balanced (as best I can) encounters with the same vibe instead of updating the stat blocks directly.

The final boss is a monster that didn't make it past 3e, so I'm just using a Deathlock, but I'm not sure if I'm missing something. The villain of the adventure's the ghost of a wizard, and the final battle is him forced into his decaying former body. The original adventure basically makes him a melee only undead, and I'm wondering if that was the point, and I'm losing something by using a spellcaster undead.

I'm a little worried about treasure too, since AD&D hands out +2 and +3 weapons like candy. I was thinking of just nerfing the +2 and higher weapons down to +1, or replacing them with uncommon magic weapons, but I'm not sure that's the best approach?

Has anyone who's run AD&D adventures in 5e before got any thoughts on the above, or tips?