I would call around for a simple drain/refill of the transmission. If the shop can do that without problems, maybe you can trust them to do more later. Otherwise, DIY!
After the 1st drain/refill of the pan, and if all is well, I would visit dealer for a pan gasket and filters kit. Some have a standard ATF pump pickup filter and others include an additional screw on filter. Using your VIN, have the dealer provide both filters, pan gasket... and service the transmission again at whatever shop you picked before, this time replacing the filter(s)....
Fluid... guessing SPIII... so either grab some Aisin SP3 from Rockauto... or use any universal/multivehicle/Asian ATF from your local autopart store that lists the SPIII spec on the back of the bottle. Pretty sure Castrol, Pennzoil, Valvoline... have compatible and capable ATFs for your vehicle.