Are there any indications that they are bad? Are you having cold or long start issues? How many miles on the truck?
In general, yes replacing glow plugs is one of the easier things to do. Just need to remove a fender skirt and make your self a tool (.020 or .032 wire) to pop off the connectors.
Check out rock auto for OEM motorcraft glow plugs, less the $10 each. If you ARE going to replace them for whatever reason, do not use after market plugs due to swelling.
2007 F-350 6.0 PSD MURDERED
6" Procomp stg II w/37" Toyo M/T's on rockstars
Stacked 7" straight cut
Pioneer D2 Nav
Sinister Coolant Filtration
Amsoil oil bypass
Blue spring "update"
BD Power hose/clamp kit
6.4 Banjo bolt upgrade