Welcome to the club man.. You will love the GS. I bought mine just 10 days ago and i love it. Mine is a 2007 model with full options list. I found it fairly quickly and just decided to go for it.
Mine too needed some attention. It has covered 60k miles and it was due a full service which i got done yesterday. Check the spark plugs have been done as they need replacing every 50k and they are a bitch to change. Im in Dublin and it cost €300 just to have the plugs changed, something about the location of the rear 2 plugs being time consuming.
A full service includes the brake fluid, oil, filters and a full diag check which will look for any faults logged on the ECU.
The dash rattle can be fixed by getting a small piece of cloth, about 3 inches by 6, roll it over a few times to about 2 inched by 2 and stull it down the dash between windscreen and the dashboard. It goes to the right side of the left speaker on the dash. This sorted my rattle.
Headlights that go on and off are a sign of bulds which are past their best, i replaced both of mine and the differrence is jugh so really worth your while getting them done.
Get the jobs done and you wil have a cracker..