I've received suggestions already regarding oil leak. Would like some input (pros &cons) about what issues I might run into if I were to drop a 98 v6 VTEC in this 2000. My obvious 1st concern is smog components and sensors, are they mostly compatible or does anyone have insight of what to expect?

 

All J-Series motors have a few pretty common leak points (in addition to the usual suspects of valve cover and oil pan gaskets):

• Cam Seals
• Front Main Crank Seal
• Oil Pump gasket
• Rear Main Crank Seal

The J30A1 in my 2001 Accord (same basic engine as you have) started leaking from the front cam seals midway between the first and second timing belt change (i.e. at about 150,000 miles); the J32A3 in my TL sprang a slow leak in the same two places at about the same mileage. Regarding when to do these maintenance items:

• I strongly recommend the cam seals, front main crank seal, and the resealing of the oil pump at every timing belt change. Fixing those leaks will require timing belt removal, so doing them while the belt is off is wise.
• The rear main crank seal is a different animal entirely. For those of us with cars featuring manual transmissions, it is pretty easy, replace the seal whenever the clutch is being replaced. For automatic cars, wait until it leaks or for your transmission to fail, and replace it then.

FWIW, I've never had one of the crank seals start leaking, but I have heard anecdotal reports of them leaking often enough the extra few dollars when performing other service is well worth the money.