Most likely, your front tires need to be "dynamically" balanced. Even if they were a short time ago, a 'weight' could have fallen off causing the steering wheel shimmy.
If the tires are new, then one could be out-of-round. . . or a wheel could be damaged. Common problem and it can be 'diagnosed' by most tire shops.
The blower regulator has probably died; do a search in the forum and you will find a number of threads on how-to-fix-it. Here's one link:
http://www.peachparts.com/shopforum/showthread.php?t=19504