1998 Dodge Caravan counter-balance shaft chain replacement

Engine Mechanical problem
1998 Dodge Caravan 4 cyl Two Wheel Drive Automatic

Wife bought this '98 Caravan about 3 years ago. It has the 2.4 4-cylinder. Has had a sort of knocking sound ever since she bought it, but local mechanics all said that it was "normal" on those 4-cylinder engines.

Has run fine but the water pump went out 2 years ago and that was a lot of fun to replace. Finally got it done though, and it ran good again.

So, fast-forward to today.

The van's been leaking oil on our driveway and, despite my suggestion that that's normal for Dodges, the missus bought a new oil pan gasket. So I look at the manual and decide it won't be toooo bad.

Got the front motor mount off, the strut, the cross-brace thingie and I was starting to get optimistic. That's when the problems started.

The drain plug wouldn't back out. It just turned and turned (stripped, apparently). So I removed the pan bolts and just carefully lowered the pan, careful not to spill. After dumping the oil I discovered a small chain link in the bottom of the pan. Uh-oh.

The rest of the chain was either in pieces around the lower counter-balance sprocket, or wedged in between the engine case and guide! (None was on the upper sprocket). I carefully dislodged and removed all the pieces. The lower sprocket was also missing two teeth (on opposite sides).

Apparently, this van had a broken counter-balance chain ever since my wife bought it (hence the knocking sound and vibration). But the manual section for replacing this chain begins: "This assumes the engine has been removed along with the oil pan, oil pump pickup and oil pump." D'oh!

So my questions are: 1) What happens if I leave the chain off, replace the oil pan gasket and keep driving it like that? 2) There's no way to replace the chain without pulling the whole front cover off, right? 3) Does the motor really have to be removed from the vehicle?

It's a shame that less than 25 bucks in parts will end up costing me a thousand dollars or more for labor if I can't find an alternate solution. Any help or suggestions gladly appreciated!

Fred B.