Are 3100 motor good motors - 2001 Chevrolet Impala

Not really.
The 3100 is a Chevy 2.8 and the 3800 is a Buick engine.
Most everything is different including exhaust manifolds, engine brackets, and wiring.

Here you go Cindy,a link on how to do it,good luck.http://www.autozone.com/autozone/repairinfo/repairguide/repairGuideContent.jsp?fromSearchPage=true&pageId=0900c15280217b69&partName=Oil+Pan&partId=0900c15280217b69

I would get another 3100 because there is noway you want to try swapping them. It won't work. A used 3100 isn't that high any more.

you would need to change a lot exhaust the computer the pumps the trans might even be different motor mounts the sub frame could be different as well so unless you have the whole car to swap stuff over its not prattical and if you have a state that test emissions you might never get it to pass

If it's Knocking, you might as well look for another Motor.

How many are in the 3100 motor in a Chevy lumina

It is right on top of the front center of the engine. (Right side of car) It has a cap on top that is marked "POWER STEERING"
If you look in the owner's Manual on page 6-10 there is a picture of the engine compartment with arrows to show you where it is. It is marked by arrow "E".

If you do not have an Owner's Manual, here is a link to download a FREE PDF version.

1999 Pontiac Gran Prix Owner's Manual

leaking what? oil coolant

Was it a code for a small or large Evap leak? The first thing i check when ever i get a car in with an evap code is to make sure the gas cap is in place and closed tight. Then i take the cap off and give it a good visual inspection. Look for cracks in the plastic or deterioration of the gasket. Replace with an OEM part if you find a problem. Otherwise clear the code and see if it returns. If it returns it can get a bit tricky as there are many parts to the evap system and the codes aren't very specific. The use of a smoke machine which pumps pressurized smoke into the evap lines is extremely useful but obviously the average DIY'er won't likely have access to one.

no your on the rite track worst case you will have a engine light on no big deal