The first place you should always look for Mitsubishi Eclipse parts is the local auto parts store. Most of these stores offer big discounts over the general dealer inflated prices. Besides better prices, many of these stores are staffed by knowledgeable sales people that can assist you in any questions that you may have. Nine times out of ten they will have the part in stock that you need and if not they can probably order it. This usually takes a day for the part to arrive and then you are good to go. Look for the best in after market parts at the auto parts store but do not expect to get the exact part that has gone bad. Occasionally, a car will require updated parts since the time it was built and these updated parts are not always made by the same place that made the original.
If you strike out at the auto parts store looking for Mitsubishi Eclipse parts or Lancer parts then you should then proceed to the dealer. The dealer is going to charge you sometimes as much as double the cost that the auto parts store was willing to take for the part. Dealers are sometimes a blessing even though they have higher prices. Dealers have access to parts that auto parts stores do not. These parts may be a bit obscure but they will be important nonetheless if you should ever have to change them. Look for better deals by making friends inside the dealership with one of the techs who may be able to get the part at cost or close to it.
In your search for Lancer parts you can also turn to used arenas if necessary. There are lots of junk yards around that have wrecked or dead cars just waiting to have their parts plucked. This works to your advantage as you can sometimes get parts from a junk yard that even a dealer does not carry. While at the junkyard, be sure to match the part to your old one. Sometimes you will run into a car at a junk yard that does not have the original motor. This would mean that you are taking parts off the car and they may not fit on yours. Also, make sure that check the return policy on parts. This will help if you get home and find out the part is no good.
Nobody likes to receive shoddy goods and a good return policy will make sure that you get the best deal for you. But buying online will not necessarily guarantee that you can send the item back for a refund or for the item to be replaced. You have rights as a customer of course but it all depends where you brought the item. If you brought it off a message board then you might not be able to get a refund as the seller will usually fob you off with excuses. But there are decent people out there willing to give you a refund.