Just checked your other thread, my bike didn't look a whole lot different form yours. I paid $800. Took me about 3 days to get it running well.
I've got a 1977 R100/7 that was sitting outside someones house here in Cali. It wasn't running when I bought it. The outside of the bike was weathered pretty good.
It had leaks around the base of the cylinders, leaky pushrod seals and the sump. I'm not sure if it has 27,000 or 127,000 miles. The barrels looked great when I pulled them. I did nothing, got some new pushrod seals. I got Viton seals instead of the factory rubber because they don't deteriorate as fast and put them back on. Got the seals from Bench Mark Works, another great source for parts. Most of their rubber parts are better quality than the factory stuff.
No smoke or problems, plugs look great. Runs awesome.
I do need to do my cam chain, because it's pretty noisy. I wouldn't do it if it was quiet. When you re-assemble it, and you have access to a timing light. Check the timing mark and see how steady it is. if it's blurred you need to replace it. Got my parts from Ted Porter's Beemershop. Everything cost me about $90. I bought chain, tensioner, spring and gaskets. I'm waiting to get it apart to see if i need a sprocket ($150.00).
Just so you know, my biggest issues were with the carbs. I would see if it will run decently before tearing them down. I would pull the float bowls and make sure the jets are clean. I did a complete overhaul on mine including new floats and slides. It was rediculously expensive, but I wanted that problem to go away permanently.
The guys posted up links to Snombum's website. Excellent source of info. Follow it, the guy is an Airhead guru... Spend some time reading through it, It pays off. Keep us posted!