Re: Class 3 transfer (In state)
As the forms do not have a place for seller and buyer your question is a bit off but just substitute transferor (seller) and Transferee (buyer).
On the forms the current registrant fills out the Transferor part whether he's a dealer or an individual so the answer to your question is yes, he fills out the parts that don't pertain to you. Since he is the registered owner he signs the form on the front.
As the other posters noted its just like any other transfer. You and/or he fill out the forms. Normally he would do the front and you the back. You get the signoff, fingerprint cards and photos done. Send all that off in duplicate, two forms, two fingerprint cards, two photos and only one citizenship certification form which you fill out and sign and lastly a check in the amount of $200 made out to BATFE, US Treasury or whatever else it might say on the forms. When the form is approved it will come back to the transferor (seller) and he will let you know to come get it. Since he's not a dealer you don't fill out a 4473 (yellow form) or anything else.
Hope that clarifies.
Frank