Blogger to WordPress import – Strip HTML?

For my website (right now viewable at http://www.031bmx.nl/wordpress ) I have just imported about 1.300 posts from blogger/blogspot to wordpress. Unfortunately years ago I decided to style my posts in blogspot by using <div>’s and <hr>’s in every individual post. On my current website, whenever someone would decide to go way back, this doesn’t look very good.

Example:
http://031bmx.nl/wordpress/?p=2832

Messy code used:

<hr height="50" color="#999999"><div style="text-align: justify;">Lees op FATbmx het <a href="http://www.fatbmx.com/modules/news/article.php?storyid=8179">mini-interview</a>, bekende onder de noemer 'FAT FAVs', met Stijn Staal. Bij het interview 4 fotootjes die je wel of niet eerder gezien hebt.</div><br /><a href="http://1.bp.blogspot.com/_F6qiMQOVmiM/Snli_EpVxnI/AAAAAAAABE0/s-1F7xKQnak/s1600-h/stijn3bars.jpg"><img style="display:block; margin:0px auto 10px; text-align:center;cursor:pointer; cursor:hand;width: 400px; height: 253px;" src="http://1.bp.blogspot.com/_F6qiMQOVmiM/Snli_EpVxnI/AAAAAAAABE0/s-1F7xKQnak/s400/stijn3bars.jpg" border="0" alt="" id="BLOGGER_PHOTO_ID_5366429266707072626" /></a><br /><br /><b>Foto:</b> <a href="http://www.rutgerpauw.com">Rutger Pauw</a>

Now I would like to be able to strip certain (or all) HTML elements for a selected amount of posts (let’s say the first 500 out of 1,300 post have this problem). Is there any possible way anyone knows about to achieve this? I found this plug-in which sounds like it could do exactly what I wanted, but unfortunately it is outdated and doesn’t work anymore. Thanks for all advice!

(Keep in mind I don’t know any PHP, just a bit of CSS).