I'll be an ass and chime in on this thread and answer the origional question.
Since you have a FWD sentra your only options for a DET are either one out of a bule bird or a GTi-R. Both the blue bird and the GTi-R were AWD cars, but the engines will bolt up easily to and FWD DE transmission. Other DET's (Such as those found in S14's or S15's) are designed for RWD cars and will not fit in our FWD chasis.
As mike said if you were planning the swap you should have bought a different car. A B15 SE (W/ SR20DE) would have been a better option. That way you would have already had the transmission, and some of the other parts will just bolt up to the DET.
Again you will find that the costs will add up. There is plenty of information on these forums about doing a swap. Check those threads out and then you will begin to understand what is involved in it. The easest swap to do is a DET into a car that already had a SR20DE in it orgionally.