After conversion... any suggestion for fixing broken tags?

[soap_box]

After converting from vbulletin I have (at least) three broken tags

all youtube videos used to be embedded with bbcodes so now they show as [youtube]o3498ghnser5[/youtube]. Same for tweets. I'm aware of how they work now but is there something for fixing existing ones?

all spoilers are broken because they accept an argument, [spoiler="about the ending of the movie"]Spoiler text[/spoiler] - (by the way I really think this is the superior way to do a spoiler tag...)

Is there some way I can maybe parse these or convert them all?