You can get from either airport (Orly or Charlie De Gaul) using either a taxi, coach, or as we do, the train. It is relatively cheap and very reliable.
We stay in a hotel near the Champs Elyssee, for about £100 pernight, but there are soooo many places to chose from you will easily get a reasonable hotel / guest house. As far as travelling to DLP, it is about a 35 - 40 minute rail trip from the centre of Paris. Whatever you do - DON'T DRIVE!! I have never done it, but it looks a bloody nightmare, especially actually in the city centre.