98 wind star poss prob.or something..?

all of a sudden for the 1st time last week my van driving at 45mph just fell out of gear then back into gear ect.. its having a hard time going over 25mph and is VERY loud and the RPMs go up to 4,000 or 5,000.. also when i try to accelerate at a light the van sputters, chokes and lurches forward a few times until it gets going. also the muffler or exost is kinda loud.. All these problems are relativley new. and getting worse by the day. Is this an easy fix of am I lookn at buying a new van?