Adding question and answer functionality – Best practice?

I’m quite new to WP and want to add a section to my WP site where users can ask and reply to questions. For this, I was thinking of creating a post category ‘Question and answer’. A question would be a post and an answer would be a comment. Using the posts functionality (instead of creating my own database tables) lets me use the administration side of WordPress.

When this is ready, I want to add a local event calendar and a review system in a similar manner (event = post in event category, review = post in review category).

Is this good practice or is there a better way?

Second question:
For the ‘question and answer’ module, I would need a page (not a WP page) where users can post there question and an index for each category. What’s the best way to do this?
I’ve seen plugins create a page with something like [showindex category=654] for which the plugin would do a replace of that text with the question content. I get the feeling there has to be a better, cleaner way. Is there?
Something that takes a GET parameter (as category number) and shows the posts in that category. Is that possible with WP?

Any feedback or help is appreciated!