Can i attach something like Self-Preservation on Celadon in Into Ithilien quest? Can i heal him with Warden of Healing?

Yes on both counts. Objective-allies function like regular allies and count as 'characters,' so they are legal targets for Self Preservation and Warden of Healing, or anything other card that uses a 'character' or 'ally' as its target.

Well, that certainly can help keeping him alive.

You can definitely heal with with Warden of Healing, but I'm not 100% sure about self preservation while he's in the staging area. He's not under any player's control at that time, so I don't think any player would have the authority to trigger the action on self preservation.

A good point, you can play it on him, but couldn't use it!

I see.

Too bad **** daughter of the Nimrodel is only for heroes. That art is awesome.

Why wouldn't the owner of Self-Preservation be the controller of it when it's on Celador? Page 25 of the rulebook tells us that players control cards they own unless another rule tells otherwise. Page 25 also tells us that players always control attachments that are on their characters, but Celador is not any player's character, so this rule doesn't apply. There is no rule about attachments on characters that are not controlled by players. The FAQ 1.38 tells us that the owner controls attachments sitting in the staging area, on locations, or on enemies. It is quiet about attachments sitting on characters like Celador, but with no rule to tell us otherwise, surely we conclude that the owner controls Self-Preservation?

After checking the rules and FAQ, I think you're right that you could use Self Preservation on Celador. I suppose that also means you could be forced to discard a Ranger Spikes if an encounter card makes you discard attachments you control.

Now that you mention it, I have always discarded Ranger Spikes if that situation comes up (when I don't have any better options). Somehow I assumed I retained control after it attached.