I disagree... british style is that the full stop (or other terminal punctuation) goes outside the quotes unless there is full sentence inside.

Wheter Fowler is British or not is a moot point at this juncture -- i was just making a point about standard usage.

If one consults any of the authoritative works on punctuation in English, it is generally agreed that letters, when pluralised, should take an apostrophe to avoid confusion, as should the word do. So, s's , do's and don'ts, etc.

The matter of the apostrophe after an acronym is one that is less well covered in most of the 'proper' books on grammar, stlye and usage, but the style used by most publishers is CDs, if you must pluralise the acronym itself. This can get tricky, however, if you have acronyms ending in 'S', viz OS (Operating System), since OSs looks silly (but not as ugly as OSes, IMO), and i think that such examples go to prove that the best solution is not to pluralise such acronyms at all, and re-word your sentence to avoid the problem.