i do swaps for 500$+ parts. that'll still put you in the 1700-2000 dollar range, because i don't put in engines that i don't pick out any more. the last time i did that, joeM's crankshaft sprocket broke in two, and grenaded the motor.
expect to pay 400-700$ for the 3L engine, 200$ or so for new gaskets/fluids, and whatever your swapper' gets for labor. if your smart, you'd buy a new clutch and a torsen LSD, but that'll run you almost 1000 for those things.
3L swaps are commonly done on the cheap, but that's not the best plan.
i have probably 3000 in my 3L swap, and i got a SWEET deal on my engine. lucky find i guess.
another thing to consider is headers. they are easier to put on with the engine out. they cost a few hundred bucks at least. so your gonna spend a few grand if you wanna do it once, or save tons of headache.