Kelly, you bring up a good point that I was about to.
Although you may not get charged duty, companies like UPS charge a MINIMUM of $40 brokerage fee. This is an absolute killer with small deliveries. The UPS delivery guy told me he had items shipped by USPS and not his own employer because it was so bad.
These crooks don't tell the US sender that their recipient will be charged the fee. They just bill the recipient when it arrives or even later, by mail.
Send your parts by USPS and be done with it. Rarely any fees. Ive had a fee a few times but very small ( no rhyme or reason).