Mack, is that thing completely stainless? Like is the back bottom and sides of the cabinet stainless?
The big thing with Summit grills is the bottom front of the cook box where the burners come in tends to corrode really bad and eventually you have issues with safety as heat and flames can exit the cookbox through the enlarged openings. If that is in good shape (once they start corroding, they go fast) then it is a steal. Even if it is tough shape, Weber should still have some you could buy to replace it and you would have a $2000 grill for a few hundred.
The burners and flavorizer bars are surely available, but if they need replacing, they will run you more bucks as well. The SS cooking grates will last another 20 years.
Disclaimer: Just be real careful with picking this up as a project. $100 is cheap, but many others have wound up putting many hundreds more into them, just to get them back to working condition. THey tend to be what we call "Rabbit Holes" and if you don't know what you are doing or what you are looking at, it can get costly quick.