Are you talking about bulbs, or are you talking about "power meters"?
Yes, bulbs can be replaced yourself. Some are in sockets, some have to be soldered in (and removing the old ones by un-soldering). The biggest challenge is not to mess up the face glass by doing something stupid, and slipping with a tool, etc.
As far as LED's go, the older Mac gear is set up using the small light bulbs, not LED's.
If it really worry's you, you can always have a Mac dealer replace the bulbs for you. But I've changed a few myself, and it's not that big a deal.
Alan