As long as the stand, lid, and firebox are in decent shape, you can get full new parts for everything else for like $150. I just re-did my 15 year old weber grill a couple weeks back with new burners, igniter, flavor bars, grates and some other misc parts, and it's working 100% like new. That will probably give me another 3 to 5 years out of it before I need to think about investing the $700 for a full up new Genesis. Completely worth it.
And their support people are great when you call them up. They can pretty much find any part you need, and give you a much better price then either a Home Depot or even their website lists. Always get your parts direct from them.