How many miles are on it? If you're getting up into the upper 100k range or so, then yeah it might be time to look into finding a newer powerplant. My suggestion (althought only my opinion, since I plan on doing this when something blows in either the trans or motor in mine) would be to look for a complete engine/trans with low miles, say around 80 to 100k or less perhaps..
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1998 Pontiac Grand Prix GTP
F-Body Ft Brake Upgrade, CAI, Buick STB, 226k miles & counting, otherwise stock