Google the internet and you can find books about refinishing firearms, Yada yada...

My recommendation would be, if you already haven't done so, is to do a KCA topic search concerning refinishing, staining, rifle care, etc.

IMHO: I would...

1. Disassemble as far down as you feel comfortable.

2. Separate the metal from wood - separating the metal from the wood is a fairly simple task.  Just remember to remove the rear sight and slide the hand guard toward the front of the barrel to prevent the hand guard from cracking by trying to pop it off.

2a. On second thought, maybe you might want to treat the  hand guard before removing.  If the hand guard wood is super dry, than, it might be more prone to cracking due to the attached hand guard clips.  You can place a quarter in the larger metal hand guard clip and a nickel in the smaller one to help alleviate the tension that the clips place on the wood after removing.

3. Clean the wood - I use denatured alcohol and a rag or very lightly use #0000 steel wool.

4. As recommended earlier, I would treat the wood with raw linseed oil or boiled linseed oil (BLO).  Raw linseed takes longer to dry than boiled.  Just follow the manufactures instructions. I've also used a 50/50 BLO and turpentine mixture with good results.  It seems to soak into the wood and dry faster.

5. Clean any rusty metal parts by gently rubbing the part with #0000 steel wool and gun oil.

6. After the wood drys and the metal cleaned I would use a firearm wax product like Renaissance Wax/Polish on both the wood and metal.

7. For leather I would recommend Pecard Antique Leather Dressing.  Great stuff that is easily absorbed by the leather with hardly, if any, change in the leather's color

Reassemble your Model 1892 and enjoy!!!

p.s. Or to keep things simple... you could just use the wax and leather dressing and call it good!