Tranny fluid question

OK, my 01 Rodeo has been leaking a small amount of tranny fluid...a red tint but no burnt smell. Got under it today barely tightened the 10mm bolts holding small pan and some on the big pan with the drain/fill bolts. I've never changed the fluid in the tranny and think it may be time to do it, since I don't know how low I am. Question is, how to fill (what tool to use) and what's the best fluid?
I don't plan on doing this every year, but unit just got paid off, so need to spend some $$ every month on upkeep. Thanks.

Hand pump which screws onto the top of a quart bottle. It's a little messy. I use the cheap Dexron III ATF at Advance Auto.
How many miles on your truck?

Right at about 70K. It's not a 4X4...just inherited it from my wife so she could get a new car. I know there's alot covered under the 10yr./120k warranty, just had to have the fuel level sensor changed about 6 months ago. I'll be sure and get everything I can done under warranty.