Do i need to wait for a few seconds before i can put my transmission into a gear while driving?

I have a 1997 ford f250 powerstroke with a five speed manual tranny and it will grind if i don't let the rpm decrease between shifts and i don't know enough about them to know if that is normal

Yes

Do whatever you have to do to avoid grinding. It SHOULD NOT take a few seconds; a pause in neutral should be enough.

On a truck that old, the synchromesh is undoubtedly worn out. Make an extra effort to match revs, even when you're upshifting. That means getting off of the gas pedal as you depress the clutch pedal. If the revs don't drop when you get off the gas pedal, there's something else happening; maybe a sticking throttle linkage.

The truck runs like a dream and nothing leaks do you think it would be worth putting a tranny in

One of three reasons.
You are not depressing the clutch fully.
The clutch is not properly disengaging this needs it stripping by a mechanic. There are various causes of this.
The gearbox synchromesh is failing and needs a gearbox rebuild.
I learned on a none synchromesh box so I still tend to double declutch.

Hesitate for a split second in neutral when changing gear as this allows the syncromesh to operate. If you are fully depressing the clutch at each change and crunching occurs it's time for a new gearbox. Or trade the car in.

Hi so here we have a 20 years old gear box which needs to be replaced. So now you need to be double de-clutching. When shifting from one gear to another you de-clutch and put it in neutral before de-clutching and putting it into the next gear. Reason is this the syncho dogs have become so worn that the gears do not align so it needs to run free briefly before a gear is selected.

You should be able to shift anytime. You have a mechanical or hydraulic problem with the clutch. The clutch pedal should be grabbing 2" off the floor. If it's grabbing high you need a new clutch. If the pedal feels spongy you have air in the lines and a leak in the hydraulic system. There's one more thing that can cause gear grinding wen shifting. The bushing that the transmission input shaft does into on the flywheel may be bad and that causes the transmission input shaft to keep spinning even if the clutch is good.

That's normal.