Quick tranny questions

I have 100,800 miles on my rodeo (97 3.2L auto) and I was looking into flushing the tranny, dropping the pan and changing the filter. To my knowledge the tranny has never been drained ever.
First of all, what I think is the fill plug (the one on the pan that is recesed about 2.5"), looks impossible to get any fluid into, do I just siphon it into the pan?
Second, I bought this Sea Foam tranny flush, will this help or hurt thr tranny? I have heard bad things about these detergents.
Any tips would be great.

Check over Ryan's FAQ's and all the other 4L30E related posts on this board, but the best way I've found to get ATF back up into the (dipstickless) 4L30E is with a garden sprayer. You can usually get one for around $10. I've also used compressed air to force ATF out of a gallon jug, thru vinyl tubing & into the 'fill' hole. That works well too, but I think the garden sprayer is easier. Fill it, pump it, shove the plastic wand into the fill hole and squeeze the trigger! I'd do 1 to 2 drain/fill cycles on yours, skip the 'cleaner' & see how it goes.
G/luck
Joel

Thanks, also found a fluid tranpher pump at Sears I'll try.