Verification of EGR cleaning

1) How can I confirm the work has been done?

Pretty hard to confirm. I think best bet would to find a shop with a good reputation for doing EGR cleaning. Which may be easier said than done.

2) How much should it cost?

I've heard $600~900 USD

3) Any recommendations on a good shop near Northern Virginia where I’ll get an honest work done at a honest price?

Leave that to other responders, hopefully somebody fits the bill.

 

A value of around 20 to 22 kPa in the car's EGR flow insufficiency self-test is typical of freshly-cleaned EGR systems. It's a decreases-with-clogging number; high is good.

Many scan tools and apps are able to retrieve "mode 6 test results", including that one. You can see several examples in the linked thread.

 

@ChapmanF already answered #1.

For #2 I would call a place called Tampa Hybrids in.......wait for it!....Tampa.
Service - Tampa Hybrids Inc.

I know they're not in your Commonwealth, but they have a darned good rep and they may even be able to recommend a more local-to-you alternative. Their quote will probably represent what a good, fair, hybrid specialist SHOULD charge.
If I were close to the beltway and counted a G3 for daily commutes I would even consider a weekend jaunt to the Sunshine state to have them do the work.
You can GET cheaper - but it may not always BE cheaper.

Preventative maintenance is like painting on a ship.
There IS no end short of the scrapyard.
At 150K you've probably done or had done all of the periotic maintenance for you vehicle as recommended by the manufacturer - but remember.......they will only provide warranty coverage for 120,000 miles - more or less.
Recommendations:
Verify all prior maintenance has been done if you bought the vehicle used.
Start changing (or continue to change) your oil every 5K.
Consider coolant changes.
Consider transaxle fluid change IF you can be sure it's done correctly.
Same with brake fluid.

Good Luck.