I need to change the main bearing and seals in the engine. Is this an easy job? Are there any special hints /tricks I should know about?

The seal is easy compared to the axle removal. It is simply knocked into the transmission housing.

Lots of tools!!! engine crane, engine stand, tranny stand, fluid collections buckets (collant, engin oil, tranny oil, transfer case fluid.
Remove transfer case, remove tranny. drop oil pan, lossen off rear eng bearing and remove slowly, remove seal materiial from upper seal have, install new seal material in both halfs, reinstall bearing and turgue to specs for bearing, install new seal and reinstall oil pan, reinstall trannt, reinstall transfer case, refill all fluids. start it up and check for leaks everyday for next week. it take 2 people to reomove case and tranny. it wiil take 16-18 hours of constant work for an experienced DYI

Remove the oil pan. Remove the rear main bearing cap. Loosen the other main bearing caps. Using a special tool that resembles a chinese finger lock pull out the top part of the seal. It's a "rope" seal. Install the new seal in the block and the cap. Replace rear cap, torque all the main bearing caps to spec. Reinstall the pan. This job is pretty big for a novice - I don't recommend you try unless you have unlimited patience.

I replaced the left front bearings and seals a couple of months back. It is not a problem but be careful as you dismantle the system and of course the reassembly of same. Be sure to replace all bearings and seals as you probably don't want to do this job twice at the cost of parts. No special tricks and relatively easy job.

Until the engine is sealed you will not know how much oil is burned. Price the parts. Difference too in whether its a 4x4 or easy access 2 wheel drive.

Check rear seal type to see if it can be changed by pulling trans and flywheel. If stick shift, probably good idea to replace clutch disc to verify not oil soaked. If automatic, oil is no consequence.

Kind of matters how much is wrong. With trans out, some rear engine seals can be replaced without removing oil pan. But if bearings are bad, on 2 wheel drive you may be able to squeeze off oil pan and check bottom of bearings.

You can do poor man's bearing job with plastic-gage. Rod bearings can probable be switched 100%. Main bearings lower cap can be serviced with upper 1/2 left in place. Not ideal, but can save from pulling motor.

Value depends on whether your Labor is free. You have a 14 Year ol truck. Depends on what you already replaced to maintain it or what else it will need. You could need rings after working on the bottom end even with a poor man's bearing job. Plastic Gage can tell you the size you need for each bearing. Then keep track and only buy individual sizes.

If you could find a wrecked truck with a good engine, places like carparts.com have a good multilist. Rule of thumb is different for each person. I would look hard at spending 1/2 of what truck is worth to fix it, knowing other things are wrong.

have you undone the cam caps then you can place the seal into position instead of banging it in

You will be replacing the seals, Piston Rings, Head gasket, Manifold Gaskets, Water Pump Seal, connecting rod bearings, main bearings and much more. Not a lot of special tools are needed, normally, but there are a few. I recommend you get the Haynes or Chilton's repair manual on your vehicle before starting this job. They will give you tolerances and torque values that you will need to know. They will also explain how far you can go without pulling the engine out as much of the work can be done with the motor still mounted in the vehicle.

Well it could be the rear of the head /Rear main bearing seal /Turbo feed or return pipe .
So get a mirror and light and have a good check to find the leak before going any further as it can be a easy job or it could be a bugger of a job so
let me know how you get on ASAP Ron

Bearings (including main bearings) as well as rear main seal require engine removal to do it correctly. If the engine is tired, then get a different one. Otherwise your determination, financial situation and skill level will tell you what you need to do.The entire job is not difficult but takes some time and you need to make precise measurements in order to get it right. (change oil pump with bearing sets) Parts prices can be found at napa online as well as numerous other places. If you need help along the way, someone here will be happy to help!

In order to replace the rear main seal u have to pull the transmission out to access it, u will need a special seal installer tool to install the new rear main "full circle seal", it u don't use the special ford tool the seal will leak again, also if there is a groove worn ion the crankshaft the crank must be repaired or replaced or the or the seal will leak again, so this is avery diff job, a 9 on the scale of 1-10 with 10 being the mos difficult.