Well, either one is a real pain to reseal with the engine in the truck. Unless it's really a significant leak, you may not want to tackle that project until you can have the truck down for a while.
To replace the front cover gaskets, you've got to pull all the crap off the front of the engine (pullies, water pump, balancer, and IP and it's gear housing, accessory brackets... blah, blah, blah). Clean all the surfaces, coat the new gaskets with a thin coat of Permatex Ultra Copper silicone and bolt it back down.
The oil pain...... opps..... I mean pan (
), you've gotta pull all the bolts after draining the oil and drop the pan on the crossmember. Then clean the mortal **** out of both sealing surfaces until there is zero oil residue. That is hard as oil will continually drip form the block while your working on cleaning these surfaces. Brake Kleen is your buddy there. Then, you need to put some Permatex Ultra Copper silcone on both surfaces and bolt it all back up. Putting extra silicone around the corners where the front and rear engine covers meet the oil pan is key to getting those areas sealed. The gap there is larger than you'd expect.
Heath