The inner oil seals are the most important pieces. They keep the gear oil and knuckle/wheel bearing grease seperate. The felts will help keep dirt and water out of the knuckle. It is more work to remove the knuckle, it just depends how bad your felts are. You'll have to change them eventually, you just need to decide if you want to tear it down all over again later. Probably better to do it now.

'86 4Runner 5" SAS
'97 4Runner
'05 Corolla
'00 F250 PowerStroke