25-65 US dollars
FIE is/was an importer. Probably made in Europe.
15-50 USD
FIE Tex Mod .22 caliber single action revolvers were first produced by the firearms import and export company in 1986. I just bought one my self and found that depending on the condition of the gun they are worth about 25-75 dollars.
Probabably 22LR. Have it checked by a gunsmith.
Assuming this is a single-shot, $50.00 in very good condition.
$100-$150.
Standard model, VG condition, $100, convertible model $150. Page 74, Gun Trader's Guide, 32nd edition.
FIE was the company that imported these into the US. They were made in Brescia Italy, POSSIBLY by the Tanfoglio Company. FIE is no longer in business- the E-15 single action revolvers seemed to be from the 1960s-1970s. They do not have a high value. Some repair parts are available from gunpartscorp.com.
50-5000 USD or more depending on specifics
$50-150 depending on condition (wear and usability) and your location (small town/country = lower end, urban/suburban area = higher end)
Sorry- but sometimes the answer is- you won't. FIE was not the maker, but the importer. Most of their guns were made in Germany. FIE is long out of business. I did check the one site that deals in used parts for older guns, and they have none for that model. If it is a small part or a screw, a gunsmith may be able to make or adapt a part to fit.