I bought the service manual for my Jem (instant download $7 US) which showed how to open the machine, clean and oil the innards. I also bought the service manual for my Janome 4900. Again, it showed where and how to dismantle the cover(s) and where to clean and oil. Definitely worth the money considering a basic service is $80+ for either machine in my area.
Remember to use good quality sewing machine oil not 3 in 1 or WD40.