70-340 is BALANCED Again........

It can be done, but... If you have the time and space, you may want to pull the engine. It's a lot easier to work on upside down on a stand then you being under it, jacking up engine, removing pan, dripping oil, and possibly missing something. If you've pulled the engine before, you have some idea how long it takes. The more you pull them out, the easier/quicker you'll get. While its out, you can pop in all new freeze plugs and check the engine over. Easier to get a good tight seal on the oil pan afterwards too. Just depends on your situation, space, parts, and experience. Having said that, this would be a great way to gain experience now, instead of when you "have to" do it in event of engine failure.
Reading your other posts, It doesn't sound like you hava a lot of room to spread out parts and have it down for very long. If it was me, I'd pull the engine, but, I have changed out a rear seal in the car, middle of winter, on my back. Don't want to do it again tho.