Looks like that solution using the power module would be outdated, now that the fluorescent dimmer is available.
The power module instructions state that the ballast needs to be Lutron. If you're going to replace the ballast, then use the correct dimmer and skip the power module.
I'd have your electrician speak to the local Lutron rep. I can't say enough good things about the local rep here - she's been very patient with me, hasn't lost her temper, and told me to get lost. Yet.
Lutron has a great website for info on controlling LEDs; wish they had one for fluorescents. Maybe they do, and I haven't seen it yet.
Edit: The RA2 Fluorescent Dimmer isn't widely available yet, just being rolled out. Still special order, 1 week lead time. The electrician will need to speak to the distributor, or maybe the rep. Have the electrician speak to the Lutron distributor first, and not the rep.
Edi#2 - I'm not certain about the Power Module - you may still need it with the fluorescent dimmer.