need help asap 2

[psd350]

my 1998 ford f250 light duty truck (4x4-auto) had few problems with it and i need your help to solve what might be wrong now.. i put truck in drive and hit gas and get up to around 3k rpms and the truck starts jerking and bucking and u can hear a thump thump thump i let of gas and it wont do it when it bucks and jerks the rpms drop while my foot is still on gas. i can put the truck in 2nd (auto) and it will do fine i took to shop and they said it could be torque converter? is this correct and how much would this run me? need your help... thanks for all the help before and also i dnt know if this has anything to do with it but ive had my service engine and oil light flash periodically while driving and they shop i took it to said that it was trying to lock up but i just wanted to make sure and yes the over drive off button works it shows up on the gauges when engaged and stay until press button again how much do you think they will charge to change a torque converter i looked up oem part and it was 250. ok well i just took it to shop and they are now saying i need whole new transmission? is this true or are they just trying to get more money i talked to a friend of mine and he told me to check the sensors in the transmission first i really need your help oh and it keeps jerking and bumping every time u hit the gas in drive no matter what. thanks for all your help well needed