Are these sealed bearings or can they be packed with grease? My pickem up has 100k and the front bearings havent been touched. Do they require maintenance or just replace them when they start to get noisy?

They are sealed units. They go down just unbolt and toss

I think you leave them be till they are shot. I got 165,000 out of my original factory ones.

I looked online quick most look sealed as Chris_tn stated.

However , you did not mention which type of truck you have IE: 1500 2500 3500 or 2wd or 4wd.
Bearings may differ with application.

,find them on line very reason prices,some place has complete hub, ur just bearing,i bought a new complete hub around $84

2016 Silverado here, I have done both of mine one at 70,000 another at 84,000 my hunting cabin has a sand road with deep water holes at times, I blame that as I had a 2009 and went through bearings and my 2000 S-10 before that. If they are warm from highway and go into deep water it seems to suck it in. I looked at drilling for a grease fitting, next time around. Pretty easy to change, "Rock Auto" is your friend. Parts stores charge 3 prices for longer and longer warrantees but give you same parts it seems. GM and aftermarket are made in Korea.

They're a sealed one piece hub and bearing assembly. Super easy to do. Take off the axle nut, 3 bolts on the back side of the knuckle, beat it out with a hammer, clean the hole with some sandpaper and anti-sieze it, in goes the new one. The new one will come with a new ABS sensor as the tone ring is incorporated with the hub and bearing assembly.

K1500 all highway miles. Ill keep my ears tuned.
Thank you!

They don't always make noise when going bad. Play in the bearing can also cause tire wear or your antilock brake light to come on.