How to use Permalinks and Redirection plugin

Hi!
I read this page about how to use Permalinks. I would like to use Pretty Permalinks, unfortunately I have still questions.

My website has at the moment 47 posts and it’s using the DEFAULT permalinks (http://www.mysite.com/?p=123). Some posts are quite popular because linked from other websites and other posts receive visitors from Google. I would therefore like to use Pretty Permalinks but also keep my page rank on search engines.

I am not sure if WordPress automatically redirects the old links and I was wondering if I need to use “Redirection” plugin for WordPress.

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QUESTIONS

– I would like to use (in the Settings → Permalinks panel) the Custom Permalink %postname% structure, so that the URL would become http://www.mysite.com/mypostname

1. Is it correct that if I would only go and change the settings to use this new custom Permalink, then the older Ugly permalink would not redirect to the new one and I would lose Page rank/backlinks? if so, “Redirection” plugin would be needed.

– When you create or update a “pretty” permalink structure, WordPress will generate rewrite rules and attempt to insert them into the proper .htaccess file.

2. “Rewrite rules”: again, does it mean that WordPress will automatically redirect my older Default Permalinks /?p=123) to the new ones with the post name that I configure?

3. I read that you need Apache web server with the mod_rewrite module for Pretty Permalinks. My Linux hosting is at Aruba.it. Would I need to ask from them if I have such Apache module or is there a way to check myself?

4. I read that if WordPress can’t update your .htaccess file automatically, it will tell you something like “If your .htaccess file were writable, we could do this automatically, but it isn’t…” near the bottom of the Settings → Permalinks panel. I cannot see this in the Permalinks page on WordPress so I guess I should be fine?

Summary

I would in few words like to know if in WP 2.8.5 redirects are automatically done for the old Ugly permalinks and if the following action points are all I need to do to change to Pretty Permalinks without losing visitors, page rank and backlinks:

* Verify somehow if Apache has the mod_rewrite module
* Make sure WordPress has access to .htaccess file.
* Update Permalink structure in WP Dashboard: Options -> Permalinks

Please let me know if I was not clear or ask me for further details!
Thanks!
Adriano