Dealer Used 3rd Party to Install Remote Starter

Now its goes into valet mode here and there. Also, dash lites flash off and on when I turn car off sometimes. Should I do a credit card dispute, paid $378. Not sure I want him toucjhing my car again, 3rd party said he'd look at it for me, don't want any new damage...

3rd Party Installer
That's not unusual, especially if you didn't get a manufacturers remote start system.
Typically, the dealer stands behind the aftermarket system and has an arrangement with
the 3rd party installer that gives you recourse at the dealership. They sold you the
remote start system at the time of vehicle sale so they have some responsibility.
Talk to your salesman, the sales manager and / or the finance manager, etc. Let
them know your concerns. At the very least the system can be removed and you get
a refund plus the dealers repair shop should check the car and give it a clean bill
of health. They are providing the warranty so they should be concerned.

R/S issues
As we don't have particulars on the vehicle year make model and the brand and model of
remote starter used, we can't really be too helpful with the specific problems you are
experiencing.

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Soldering is fun!

2006 Buick Lacrosse - yes, the warranty on the invoice basically says they're not responsible, however I did not sign the disclaimer.
The dash and radio display started flashing on and off when turning car off after installation. Are they related?

flashing dash / lights and radio, could be the remote starter flashing an error message.. I would let the 3rd party installer have a look first.   

And Seriously, you have a 13 year old car I wouldn't be so quick to blame the installer. It could be User error, or an issue with your car