ok so here's the deal i just bought a 98 Grand Cherokee and went to get an oil change while i was there they told me that it was very hard to get the oil out and that there was a lot of sludge buildup and now it has white smoke coming from the tail pipe. any ideas?

Not good. Was the purchase from a (reputable) dealer?

Take it back to the crook you bought it from.

be afraid but if it was a 4.0 you can always get a 4.7L long block.. that's what i'd do. but your motor is toast bud i'd be surprised if you didn't hear any knocking