i work at best buy so i can help answer some questions...
if you already have cable/dish/directv/satellite etc. you DO NOT need a converter box.
if you have been using an antenna and only watch the basic channels you WILL need a converter box. you will need to use an antenna with the converter box. the newer LCD tv's already have a digital tuner built in so you won't need the converter box.
converter boxes ARE returnable and you do have the option of getting the $40 coupon through the government (DTV.gov). best buy has 2 different brands of converter boxes right now (insignia and apex) the insignia one is 59.99 and the apex one is 49.99. so, if you want to use your coupon with it the apex one would be 10.99 afterwards, which isn't too bad especially if you're planning to buy a new antenna with it.
as far as TV's, our store had a 32" samsung LCD for under $500
theres also a lot of good deals depending on the size you want. PM me if you want more info
OH! i forgot.. the government extended the digital conversion until june but MOST broadcasting companies have already made the change. it just depends where you live i guess. good luck!