I looked at the FIS results. Looks like his Calgary olympic year was his first international year. He was third in the combined and like I said I think he won the slalom leg to acheive that!!
Given he was in the extra olympics at Albertville or Lillihammer (I forget which it was) and given that he would likely hang on another 2 years he has to be close to setting a record for most olympics skied in. If he makes it that would be 6 by my count. I'm assuming he didn't miss any due to injury. Guys who ski this long usually go injury free. Stenmark must be close as well but he didn't have the advantage of an extra olympics.
Lillehammer was the odd olympics to facilitate the split with the summer olympics. Ingemar actually only participated in 1976 and 1980 as far as I recall. (I don't think he was in Sapporo in 72). He was not eligible for the 1984 olympics due to his "professional" status.