how do you go back to auto sync without loosing content

(I have a 2nd gen i-pod nano) My computer crashed and when I got around to re-loading the lastest version of i-tunes, I opted to load content manually. However, I now seem to have a different library on on my devise than the library that appears on i-tunes. On the summary page I can see I have "songs" and "other content"; I don't seem to be able to locate or access the "other content" (classes in mp3 format that I use for work) When I attempt to turn off the manual sync I am prompted that I will lose the content on my device. Since my device is the only place I have everything that was on the previous version of i-tunes, I'm not willing to do that.