Sewing machine....
I've never seen one that wasn't fixable unless it's a bottom of the line Walmart disposable. (mechanical machine) I grew up in a laundry and sewing machines were a daily dealing. Take yours outside, if it's mechanical, expose the moving parts (top and bottom), remove thread/bobbin, blow it out with compressed air if you have a way. Firewall the throttle and blast all bearing holes with WD-40. Soak up all splatter/drips with paper towels. You'll hear the machine get happy.
WD-40 will evaporate and leave a fine machine oil in it's place. Use good sewing machine oil until it needs cleaning again. Load the thing with thread....use good stuff like Guttermans poly for outdoor wear....medium needle, and play around with some fabric, bobbin tension, thread tension. You'll get it just like you want it.
(disclaimer...if your's is an electronic machine, oil ONLY the bearing points assuming they aren't sealed! If the 'stepper motor' is out of time, or the firmware is corrupted, you're toast. Go find an old mechanical! )

Fabric:
Absolutely!!! Those old rain flies are a good way to start and practice. I cannibalize fabric all the time from old projects or discards. Iron your seams/hems before sewing. One nice thing about NOT using silnylon is that you can make a "hot tacker" from an old soldering iron and eliminate pins. I hot tack my kites together before sewing. Saves tons of time. Sound like you are on your way!