You can sell the improvements that you built before you got the wonder. If you built it yourself, you get the option to sell it; if it is wonder-built, you can't sell it. If you are playing for 100k, beware: free temples don't get culture doubling, so don't sell any temples you've built previously. Preserve Random Seed does guarantee the same results if you do exactly the same sequence of things. However, if you change the order in which you do things, the outcomes may be different. Additionally, talking to the AI accesses the RNG (deciding what to say to you), so if you talk to the AI a different number of times than you did the first time, you can change the results of everything after that.