Not sure how old school it is, but it was first published back in 2E days. The original version is called "Tragedy in the House of Brodeln" and the 3E version is called "Aldriv's Revenge"
It has a murder mystery, some dungeon crawls, some interesting monsters, some excellent NPCs and a good final villain. I was a player in the module back in 2E days and it kickstarted the greatest campaign I had ever been involved in as a player or DM. A huge group of PCs (8-10 of us) and a great DM. I loved it so much, that when I ran my own 3.5E campaign that ran from Fall of 2007 until Spring of 2009, I picked this same module to DM. I had some different twists and turns, of course, and the campaign went in another direction after Aldriv's Revenge, but that was a great campaign as well, and for a completely different group of people/players.
It would probably take you from level 1 to level 3 or 4, but there are some nice loose ends that the module leaves the PCs to tie up at their leisure that could easily get them to level 5/6 range.
Supposedly, Red Hand of Doom works best if the PCs are attached to the area where the hogboblins are going to attack & overwhelm. The town of Yelden could work very well in that regards. There is an elven forest nearby, plus it's not far to a nearby mountain range, etc, etc.
http://www.amazon.com/Aldrivs-Revenge-Dungeons-Dragons-Adventure/dp/1889182567/ref=sr_1_1?ie=UTF8&qid=1400627167&sr=8-1&keywords=aldriv%27s+revenge