Hooking propane grill to whole-house propane tank

I called my local propane supplier and they tried to talk me out of hooking my Weber S-420 to my house propane tank (500 gal). I had my builder plumb the line outside. I understand I'll need a shut off valve, but they said it'll be about $150 to convert the grill. Apparently they want to take off the grill's regulator and black plastic nut. Is this needed and does anyone have any experience with this? I have a hard time finding stuff online that doesn't have to do with natural gas.

Follow Ups:

• Re: Hooking propane grill to whole-house propane tank PFSmith 21:35:18 2/22/09 (5)
  • Propane Grill to House Propane Jason 18:51:14 2/23/09 (4)
    • Re: Propane Grill to House Propane John 16:56:22 2/24/09 (3)
      • Re: Propane Grill to House Propane rubicam 19:40:17 2/26/09 (2)
        • Correction for rubicam John 17:10:50 3/20/09 (1)
          • Re: Correction for rubicam Matt 18:54:32 3/31/09 (0)

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