is it normal to have some movement up and down at the rear pumpkin where the drive shaft bolts two the pinion

 

I'm not 100% sure, but I think a little bit of play is okay to allow for the driveline components flexing angles as the truck moves.

 

If you mean where the pinion shaft and flange to bolt your drivshaft exits the pumkin.....then no.
A pinion bearing surrounds the pinion shaft exiting the pumpkin and seals it tight with the pinion bearing seal.
There shoiuld be no play here.
Are you getting oil splashed up around the pumpkin and fuel tank.
Classic signs of a pinion seal going.
Also if you have play here, do you have a noisy drive train?
Al.

 

no noise but funny vibration sometimes and oil leaking on bottom of pumkin am going to change seal and yes if i wiggle the back of the drive shaft where it meets the pumpkin i have a little play there so should i change the bearing and seal and how hard is it to change the bearing.

 

Well from what you have just told me, the seal has gone and I would definately say the bearing as well.
You can replace these yourself and there is a write up on how to do it on this board. Do a search and reseach the problem.
I will say that if you need to replace the pinion bearing, it is relatively straight forward, but must be exact in it's implementation.
A turn too much on the new pinion nut and your bearing again and possibly rear, is toast.
Someone will chime in with the "how to's" on this, but I believe you have to unbolt the driveshaft.
Remove the pinion nut counting exactly, how many turns it takes to come off.
Remove the pinion seal.
Remove the pinion bearing, then place the new bearing into the diff and tap it squarely back into position which is critical.
Then the new seal and then put the new pinion nut in place and tighten it back to exactly the same amount of turns you did to remove the old one, plus I believe half a turn extra.
That is how I remember reading on here people do this instal.
Hope this helps?
Al.

 

You go, Al! Yep, sounds like a pinion bearing or two is shot. If you jack up one side of the axle to where you can spin one wheel and move it forward and back you can check the drive shaft play. If you see ANY play up, down, left right ... basically anything but circular, the pinion and/or bearings have failed.