HELP!! Lifter Problems

[hobsiscool]

Ok so when I bolted on my new head, I had all the rockers installed and adjuster, got the engine running, etc, etc...I hooked up a vacuum gauge to it recently, and noticed the gauge was jumping, so I think, must be a valve out of adjustment. When I pop the valve cover off, I notice one of my rockers is free as a bird, and my pushrod has fallen down...I obviously have a collapsed lifter correct? I'm running a 250 inline...I've read that I would need to replace ALL lifters AND camshaft if I have to replace one...is there any other solution??

I've also read that perhaps I just have a clogged lifter, and perhaps it can be remedied...in order to get to them, i'd have to take off the push rod cover on the side of the block correct? Would I need to drain off any coolant to do this first?

Someone please help, I was so close to being able to take the truck for it's maiden voyage, and now it seems i've taken 12 steps back.

Thanks in advance!