A flash intro only slow down site loads and anoys people. The idea of a site is to supply info as quick as possable before the users gets bored.
If you must ahve flash try using something like firestarter which lets you do it in seconds. You can get a free down load to try it. There is also loads of flash sites out there that give some flash which you can customize.
Remember some people only have 56k and may well get Ped off with flash intro and decided to use kryptonit