Camshaft Bearing Replacement

I have a 2003 Disco with 305,000 miles and recently started knocking after she warmed up.
So I took the cylinder heads off, as I was getting a water leak on the backside and needed to replace the gasket.Inspected the rocker, lifters etc. and all seemed in good working order. So removed the oil pan and found a camshaft bearing split in two and folded over. So I have removed the camshaft, without removing the engine from the truck and found that the 4th bearing is gone. Not a mark the camshaft or lifters. Have ordered a new camshaft, bearings and lifters.

I need to install the new camshaft bearings. Does anyone have any advice or tricks to install them. I assume the crankshaft has to come out. Also the oil conduit to the 4th bearing may be clogged and how might I check for that?

Any help is greatly appreciated.

Mark