Wow, I never knew anything about that, I've seen the one where Will presents backstage stuff loads of time, but that's news to me.
This episode where Jeff presents isn't mentioned on the guide I refer to (http://www.tvtome.com/FreshPrinceofBelAir/guide.html), so I'd love to know more details about it.
As to the part where Will gets tossed in the van, I vaguely remember someone mentioning that they were considering scrapping the show at that point, I could very easily be wrong to, so don't quote me on that. To be honest, why would they have that bit at the start, and then a perfectly normal show afterwards, seems a little weird to me.