Honeywell Thermostatic Radiator Valve

RadiatorFan

I have a Honeywell thermostatic radiator valve, with a dial that’s mounted on the wall, on one old Crane radiator. I think the Honeywell model number is T104b. 
A contractor working near the radiator accidentally broke off the plastic piece attached to the radiator. 

I’d like to know (1) if I have to replace more than the valve part, (2) if it’s just the valve, how difficult is the repair? Do I need a heating professional or plumber? 

The rad is part of a two-pipe steam system in a 12 unit two-story building that is 94 years old. The building has about 40-50 radiators and I think mine is the only TRV in the building. It was installed over 15 years ago (installer is no longer around) and worked great the entire time
I’ve read through other discussions but can’t say I understand enough to describe to a pro, but like to be knowledgeable when I call one.
Here are pictures.
Thank you for any help. The forum is so wonderful and has been so helpful as I’ve been trying to educate myself about our heating system these past years. 

JUGHNE

That plastic shell might be replaceable....maybe.

Or you just need a new power head and wall tstat.

Unscrew the large ring and the rest of the broken pieces will come out.

That plastic gets cooked over time and becomes brittle.

Or you could go with the valve mounted tstat. It mounts directly on the valve.
It will control a little differently because it is close to the radiator.

The plastic in it will also cook out in some years of use.

Alan (California Radiant) Forbes

I would just replace it. Unscrew the old head and screw in the new one.

Whatever you do, don't cut the capillary tube that's filled with alcohol.

https://www.supplyhouse.com/Honeywell-Home-T100B1035-Remote-Setpoint-and-Sensor-for-V100-and-V2000-Series-Radiator-Valves

RadiatorFan

Thank you, I’ll give it a try!