Just bought an LS, concerned, help!

This is my first foray into american motors and I'm already skeptical. Picked up the 01 LS yesterday with 81k on it. Driving along and try to accelerate and it feels like the car is mis-firing. I feather the pedal and it eventally comes up to speed. Attempt to past a car on the freeway and again, the car falls flat on its face. Attempt again and it does it fine. this morning Im going out for coffee and try to cross an intersection and I swear I almost got creamed by a bus. Car refused to accelerate. Please help, I have been reading about all the transmission issues. I still want to believe that the car needs a good tune up. Are plugs platinum/iridium? 60k replacement or 100k?
I called the dealer back and of course he says nothing was wrong with the car when I left there, granted I could not go more than 30mph on the back roads where I picked it up. What else should I replace when I do the plugs?
I read that the valve cover gaskets, pcv and coil packs should be checked at this time. I'm trying to find the guy I sold my 97 Celica to and see if I can get it back, it has 140k on it and works like a dream.

if it is mis-firing - then likely it's time for new coils, plugs and new valve cover gaskets. There was an issue with the original VC gaskets whick allowed oil to leak into the spark plug wells - causing mis-fires - usually more noticable at the higher rpms.

the LS has been a good car overall. don't american motor companies for this. come on it's a used car. it sounds like a simple problem to correct (prolly why the original owners sold it) give it a chance b4 you chase donw the old car you may find you like the american ones now (since they are more foreign than the so called "foreign cars").

Replace the vcg, plugs, and coil packs and all your problems should be fixed. I had the same problem when I purchased my LS. I was scared to death that what I was experiencing was a trans. issue. When these things were replaced the car ran/runs like a dream.