I'm not in a guild, and I remember a couple years or so before I was able to sell whatever point for like 25 fg or something (no idea what, or if anything it'd be worth now)

I'd join guild, do MQ, then get paid the fg, then leave guild. Is this still allowed?

yup

You are no longer required to use a Mediator when buying Guild Points, But may always request one.
* If you are selling Guild Points, You must make it clear in your post what class you are and how many Guild Points you will get for a pass/fail.
* If you are offering, Be sure to make it clear if you are offering FG on each Guild Point earned, or on pass/fail.

I assume it gets posted in ladder slasher trading?

thanks for info

Yes,sir!