I replaced a couple on mine (key busted off or something) back in 2013.
IIRC the p/n can be found by removing the latch.
Removal is easy just pull the simple flat bar clap that pinches it to the door.
Ive not hand any problems with the finish - replacing them all to convert to stainless/chrome would be pricey....that said I'll buy at least a few of your old ones.
Mine are C5's and I replaced them w/ c5-13-45's - theres is a logical science to their part numbers - and while I dont recall it now, once I figured it out it was easy to decipher.
I bought 3 c5-13-45s (black no key) for 44 bucks from a seller on EBAY
'04 Haulmark (M42386) 42', 2 slide, 10kw - Pictures
'04 F350 CrewCab Longbed 4x4, 50g aux tank & gear vendors dbl over