You will have to contact Sig. They offfer a sn letter for a reasonable fee.
no
Possible, but, not recommended
Stainless Steel frame
50-400 usd
100-350 or so
100-500 depending on specifics
Depends on what is wrong with it- and you did not give us a hint.
It is possible, but, not recommended
http://www.sigsauer.com/CustomerService/documents/SIGARMSP232OM.pdf
100-800 USD or so depending on specifics
At $100 I would suspect that the firearm is either stolen or has been used in a crime. I would be highly suspect of such an item. The normal retail price of a new firearm is well over $500, and a good used price would be $350 or better.
No. There are many low-quality pistols in .380, but this is not related to the caliber. If it is a reliable model, it won't jam more than any reliable larger caliber. Badly designed and sloppily made pistols will jam, quality pistols will work perfectly. For instance, SIG Sauer P230 is chambered in .380 and is one of the most reliable pistols out there.