Egret, there are dozens of good fabric sources on the web.  You might enjoy Sewing World www.sewingworld.com  It is a disucssion board for people who do various kinds of things with fabric from garment construction to quilting to machine embroidery to different crafts.

Also, for fabric here are a few more:

www.fabric.com   lower prices but sometimes very good deals
www.michaelsfabrics .com     higher end, fantastic quality

It might be helpful to know what kind of machine you have, the model, how old it is and whether you have the owners manual.  Some machines are just plain trouble.  Other machines, once you get them threaded, work just fine.  Maybe you, or your grandma, know someone else who can get the thing threaded up for you.

You can try the yellow pages under Sewing Machines and Sewing Machine Repair.  Some repair shops will repair any brand others are specific to the brand(s) sold by the shop.  I hope your machine is still repairable but I'd be careful about putting too much money into a seventies machine.

I would agree that the needle may not be in far enough.  Loosen the screw around the needle holder and push up the needle.  Singer makes, or used to make, its own brand of needles.   Needles are not generic.  Singer are different than, say, Schmetz Needles which can be used in several machines.  I want to say Singer needles are ever so slightly longer, or at least this is as I remember.   

I buy lots of fabric on line.  What kind are you looking for.

Here are some good sources:

www.equilter.com  (quilting, fashion fabric, home dec)
www.keepsake quilting.com (all kinds but emphasis is on heirloom)
www.sewingstudio.co m  (fashion fabric)
www.emmaonesock.com  (trendy fashion fabric)
www.vogue fabrics (fashion fabric)