Just found this reference on the Web... I can't comment on its accuracy and/or utility, but its something you might want to check into if you still need a service manual.
The reference is:
String Trimmer and Blower (1997 and Prior) Service Manual
and you can find it at Clymer Manuals on the Web:
http://www.clymer.com/Book.aspx?bid=733&title=String+Trimmer+and+Blower+Repair+Manual
The blower should be cheap to fix yourself if you're handy, and many small engine repair shops carry parts for vintage tools and engines. Most are helpful guiding you to the correct replacement parts as well. Just look for a shop that's been around awhile. It will improve your ability to find the needed parts, as well as service advice.
Gary, Raleigh, NC, November 2009