This is certainly possible, though I don't have any example code. The interrupt flag you need is called TXC (transmit complete) and it's action is (briefly) described in section 26.6.2.5 of the family datasheet.
There is one interrupt vector for each USART, you have configure the INTENSET register for the events you want to raise an interrupt, TXC in your case. Additionally you will need to configure the NVIC interrupt priority (NVIC_SetPriority) and enable the interrupt (NVIC_EnableIRQ) for the USART you wish to use.
In the interrupt handler, you need to check which event has caused the interrupt by reading the INTFLAG register and testing the bits. You then should clear the interrupt by writing a 1 to the bit.
Note that if you want to send multiple bytes, then waiting for TXC after each one will not provide the best throughput. The data register is double buffered, so you can load the next byte to send whilst the previous one is being transmitted, and you should use the Data Register Empty (INTFLAG.DRE) interrupt in this case to load the next byte in. You'd likely only want to use TXC on the last byte in this case, so you can tell when it has been shifted out.