Pay the extra $50. Depending on what equipment you currently have, upgrading from a legacy system to a DishPro/DishPro Plus will probably incur more costs than you will pay for the installation. That installation will include a new LNB if necessary, cabling to the second TV if necessary. any other small odds and ends that may be required for the installation. Unless you have a very unique situation, the $50 will be well worth it.
If you are still interested in doing the install yourself, please post the type of Dish/LNBs/Switches installed in your system and we can try to help you from there.
Edit: After reading your post again, I see that you have a Dish 300. If this is the case, you definitely want to pay $50 for the install, as this should include a new 500 dish and a DPPlus Twin to run the 322 with a single cable. this dish from dishstore.net costs $75 alone (
The Dish Store - Powered by Metro25). Save yourself the hassle, you will actually be getting all the channels you are paying for.