According to my sources, a pan drain on a U241E transmission removes 3.7 out of 8.7 quarts. Recommended fluid is Toyota T-IV.
The T-IV fluid is considered to be lifetime fill under most conditions. The anti-wear additive package should provide sufficient protection for the life of the unit.
However, I'd still do a pan drain every 30,000 miles to maintain optimal shift quality. While the fluid may be OK in terms of anti-wear protection, shift quality will suffer if a partial change isn't done periodically. However, the increased fluid changes may only have a minimal effect on transmission life, at best.
This transmission has a conventional pan, along with a media filter. AFAIK, the newer Toyota AW "U" series transmissions requiring Toyota T-IV now contain a media/felt filter. The pan still has a drain plug though. Drain the transmission pan via the drain plug. Refill with new Toyota T-IV. If desired, drop the pan and change the filter, but I'd wait until 60K. Toyota dealerships will tell you that the filter is of a mesh filter, but this is no longer true. Drivewire has the OEM filter, but it costs $45.
Transtar, which is a major parts distributor for transmission shops, should have the transmission filter. Look for SPX/Filtran branded transmission filters, not the China knockoff ones. Mention U241E transmission and they should know what you're talking about. Bulkpart has the filter, but given the ridiculously low price ($5), it's probably the China junk.
PS- How did the ATF drain/fill go on the Civic?