A couple of days ago, I noticed that Winamp has a Replay Gain feature...

I'm thinking, is it better to use that instead of using MP3Gain on my mp3s?

If so, can you give me some info on how to make it work?

And most important, how should I slide the db slider in order to have gain at 89db?

Please, don't tell me to use foobar's Replay Gain 'cause that's not gonna happen

I don't use Winamp so I don't know if it has a replaygain scan function like foobar2000. However I do know that the MP3Gain program has an option to just write tags. Unfortunately it will write the analysis information to the MP3's as APEv2 tags. If that isn't a problem for you, then I would try MP3Gain, otherwise you could try foobar2000