1990 Ford F-150 4.9L F-150 1990, Can freeze Plugs be replaced

Engine Cooling problem
1990 Ford F150 6 cyl Two Wheel Drive Automatic

I don't have a clear understanding of the history of this truck. The owner is offering it to me to use if I can fix it. I really need a vehicle now for work, so I'm trying my best to get it going.

After doing a number of repairs to the truck, and getting it going sort-of, I discovered two leaking freeze plugs, the front and the rear (on this inline 6). The leaks are too bad to ignore, and the rear one pours directly on the starter. (The truck is missing the radiator cap; this must be because the former user was adding water constantly and didn't want to pressurize the cooling system.)

The freeze plugs are very hard to access. I'm not even sure it's even possible to reach them with the engine still in the truck. So I'm wondering, is it possible to change those freeze plugs without removing the engine?

It makes a difference. I'm not really an auto mechanic, and I don't have a lot of tools. But I have a mechanical aptitude, and if it can be done, I can do it. But I need to know if it's reasonable to change them without removing the engine. I need to know how to proceed. Someone with experience with the engine would know.

I have to decide on a course of action. Has anybody changed those freeze plugs?

It's a 1990 F150 with a 4.9L fuel injected engine.

~~ Nehmo