Ginger_Ale said:About your first question:
I don't, I like happiness and science. Unless I get all 8 luxuries and get a marketplace (20 happy faces), I wouldn't consider selling temples. Anything with culture is a good buy (usually). The times I will sell improvements is when I build a wonder like Sun Tzu's (free barracks on every city - doesn't run out). All the barracks I have, I would sell them to get lump sum, and next turn I'll get more gold per turn as its maintanince cost goes away, instead of just getting more gpt. (Make sense, or are you confused? :crazyeyes: ) Same goes for other wonders like that such as the Internet and Research Labs.
ynone - keep in mind that those improvements' benefits stack, so you'd only be hurting yourself. Also, as Cathedrals need Temples, they might disappears when the temples go bye-bye. I've never actually tried this, so I'm not sure. In any event, it's worth the upkeep to keep the improvement around. Your culture will always go up, and after 1000 game years the culture doubles.