I need to replace the oil pan gasket on my 1969 Chevelle Malibu with a small block 350. The Haynes manual indicated that on some of the 350s on this Chevelle, the engine has to be removed to change the oil pan gasket. Is this true - that would be quite a bit of work for a $25 gasket.

For 68-72 Chevelles with a SB, the pan gasket can, repeat CAN, REPEAT, CAN be replaced with the engine in the car. But I assure you it is a TRIPPLE B!$&H!!!.
Before starting, I'd park the car wherever you are going to change the gasket for a few days, because when you pull the pan, it is going to drip, drip, drip oil.
First, the front counterweight of the crankshaft must be up, which means the timing mark on the balancer needs to be pointing down.
Next, remove the distributor and disconnect EVERYTHING, mounts, exhaust, fuel line battery cable, etc.
Then the engine has to be jacket up to the sky, no, that's wrong, to the moon!
If your next door neighbor is a pastor, close the garage door so that he can't hear you.
Then proceed to remove the pan. Make sure everything is clean, clean, clean and wipe all gasket surfaces clean and dry with something like brake cleaner.
My preference for a new pan gasket is the Felpro 1-piece. The instructions say NOT to use any sealer. BALONY! Use the Ultra copper or black RTV at all 4 corners-------------BOTH sides of the gasket.

Many people say, and I pretty much agree, it is just as well to go ahead and pull the engine. Personally, I don't pull the engine, because I CAN pull-replace the pan with the engine in the car, but it's a major pain!

Some guys say they have even been able to pull the pan on a BB with the engine in the car-------------I've never been able to do that with a BB.

Tom sums itup in a nutshell. I've done in it on the 454 in my 70. There were colorful words involved, but it is possible.

I did it on my '69 Malibu 350 to replace the rear main seal. PITA but so is lot of things on Chevelles. I might add you should pull the dist or at least remove the cap and at least loosen the rear trans mount bolts before jacking the engine up. I jacked mine up by the harmonic balancer (block of wood bet jack and bal) to keep from damaging the pan, then placed blocks of wood between the upper and lower halves of the motor mounts. You sure don't want anything to slip with your hands up in there. As DZ said, use plenty of gasket sealer esp at the corners. You don't want to have to do it over.

I jacked mine up by the harmonic balancer (block of wood bet jack and bal)
This is such a bad idea for so many reasons. If you have access to a cherry picker, use it.

This is such a bad idea for so many reasons. If you have access to a cherry picker, use it.
Must not be too bad of an idea since the '69 GM Chevy Service Manual recommends it and even shows a picture of doing it on a Nova or Camaro with a special tool. I use a block of wood I cut with a semi-circle cut out of the top to fit the balancer. But I agree a cherry picker is probably better.

Ide pull it.