Welcome to HD universe !
I would like to say to the person who made this post,just as others have said ,Yes you will need new dish and receiver,but that wasnt to big of a Job at least at my house for Dish to switch over.
However I wish I had known alot more information about High defination before making the jump as soon as I did.Please realize once you see HD programming you will not like watching too much in SD,and depending on your Tv some SD will look really bad.Please note that even though a channel says HD version ,unless show was shot in HD or has been upconverted it will at least at first not look that great.And you may need to keep adjusting ratio from time to time.However HD channels programming even if not HD is significantlly clearer.
I wish I hadnt gotten rid of my SD TV as some shows I prefer to watch in that format and digital looks great on those old sets.But keeping all this in mind dont skimp on buying a new HDTV do your homework like I did and find a store that allows you to bring back if you get it home and dont like how it looks.I search high and low to find a good tv and decided to save 200 and I am now stuck with a piece of crud until I can go out and buy another HDTV.
To sum this up HD is great,but dont expect every show on every HD channel to be HD,sometimes only first showings of programs are in HD,then Future showing of same program is back to SD version.WGN is good about that one.
I am happy with HD but it still has a long way to come before everything is in crystal clear HD.
I know this problably wasnt information that the poster was asking for ,but any information is always helpful,whether they use the information to their benefit is up to them,just putting it out there.