Hello,Welcome to our site and thanks for your question. My name isXXXXX and I will do whatever I can to help you.
What an interesting old conversation-piece you have! However, repairing a machine that is over 30 years old is rarely worth the money. There are numerous machines on the market that will do far more than the the simple sewing that your 5710 does for less than the cost of even the simplest repair. My repair center charges $75 to bring the sewing machine through the door for diagnosis of its problems, plus parts and hourly labor. You can find many simple machines like the 5710 for $100 and up. You might want to check your local sewing center for machines that people have traded in on newer computer models that do everything but cook dinner for you.
If you do decide on a repair, choose a shop that credits some of the repair diagnosis cost toward the purchase of a new machine.
You can find manuals on ebay for less than $10 such as this one: http://www.ebay.com/itm/Viking-5710-Sewing-Machine-Manual-On-CD-/370682950575#ht_2734wt_958
thank you, XXXXX XXXXX I need to know. short not too expensive.
You're so very welcome!