Help, I am new to this.

[357/38]

I just purchase a Winchester 1873 reproduction Sporting color harden case model/ 357/ 38.
Many questions
1. What oil and clearer to use?
2. What type of ammo should use?
3. is ok to use round nose lead bullets?

[River City John]

Flat nose bullets ONLY.

Ammo to Cowboy Action Shooting specs or equivalent. NO +P rounds.

Many oil and cleaning products out there. Experiment. I use Ballistol, either mixed with water, 2 parts Ballistol to 8 parts water, or used straight. (I use Trail Boss powder in my reloads.)


RCJ

[Abilene]

Right, flat point only.  You will hear of people who have used round nose and got away with it, but it is not recommended.  If you use .38's, they usually need to be at least 1.45" long or the action will jam.  That length varies some so YMMV.  Here is an article by Pettifogger which will explain how the action works and how to determine the minimum length needed for your ammo:
http://www.theopenrange.net/articles/togglelink.pdf

I like Ballistol because it is both smokeless and black powder friendly.  I use it like River City John diluted with water to clean, but only for black powder.  For smokeless, use it straight for cleaning.  It seems to take more patches to get the barrel clean when shooting smokeless than some other cleaners, but that's okay.  Always use it straight for lubing the bore after cleaning.  For smokeless only, there are a lot of good ones.  Rem-Oil has a lot of fans, though I've never tried it.  Break-Free CLP as well.

Enjoy your '73!