well if your taking about the door seals, they are a peice of cake. I have replaced them on my 83 bronco. they just slip around the pinch weld of the door opening.
The tailgate weather stripping is just as easy. just some screws that hold the upper glass run into place.
i've replaced alot of weather stripping on my bronco, none of it has been really hard. It makes the interior way quieter and no wind noise, also the doors and tailgate don't rattle when you close them. The only weather stripping that u need to leave to the professionals is the windsheild calking.
http://www.dennis-carpenter.com/pdf/67-79Truck.pdf
check that site out for almost everything. they have good prices.
Jeffs bronco graveyard or lmc truck has alot also.