I have a 7.3 powerstroke with just over 100K on it. I have done only the following

replaced the fuel filter
replaced the air filter
lubed
oiled

Given that what should I be doing at this point?

I plan to change trans fluid
What should I be doing to the glowplugs?

She runs great and that's how I would like to keep her, so what would you suggest?

Thanks!

What year is the truck? Auto or manual?
I would think about changing rear differential fluid, getting injectors cleaned, etc.
I don't think there is anything to do to the glow plugs until you suspect them causing a problem.

The vehicle is an Excursion and an automatic. The year of the vehicle is 2000

Other than what I've already said, not much comes to mind. Keep an eye on the battery cables for corrosion. At 100k, she's just hittin' her stride. They last a good long time with good care. I would suggest searching for a diesel specific site for more comprehensive information.