I recently had the timing chain, gears and tensioner, water pump and radiator replaced by a licensed mechanic. Within days of getting the truck back i developed an oil leak then the truck had no power unless i mashed on the gas. I returned the truck to the mechanic and after a longer than necessary wait he said it was the harmonic balancer, after replacing this he says the bearings are bad and the truck has a very limited life left. My question is could anything he did have caused this issue? Please help, I have a roll bar, lights and numerous accessories i wanted to put on this truck, the body is solid and after having new brakes, custom rims and off road tires I had planned to have the truck for awhile.

 

Sounds a bit off.

Where is the oil leak?
Front, back or side of engine.
If in the front then mechanic didn't get a good seal on the oil pan/timing chain cover gasket or on the front main seal.

Why was the timing chain replaced?
That is one thing on the 4.0l OHV engine that rarely needs to be replaced.
Water pumps do need to be replaced as normal wear and tear
Radiators can last the life of the vehicle if coolant is changed every 2 years, but still not an expensive repair.

Bearings have nothing to do with 'lack of power' they will make a knocking sound similar to exhaust leak, but engine will still have normal power.
Same with harmonic balancer, it won't effect power.
First sign of a bad balancer is a squealing from the fan belt(serpentine belt), and if you look at the balancer with engine running you can often see it wobbling, or look at the belt tensioner and you will see if 'jumping' up and down

If timing chain was installed one or two teeth off then you would have a lack of power since compression would be lower, slow to rev and general lack of power at all RPMs.
Compression test should show 160+psi per cylinder, if you get 120psi or less then timing chain is wrong

Mechanic could have broken harmonic balancer when removing it to do the timing chain, have seen some use the wrong type of puller(jaw puller) to get a balancer off which can break it.
Harmonic balancer is made up of two pieces of steel, a center hub and an outside ring, these two pieces are held together by a hard rubber "gasket", this rubber absorbs the engine vibrations, when you need to remove a balancer you must pull it off using the hub, there are threaded holes in the hub just for that purpose, if you use a Jaw type puller on the outside ring you can break the rubber gasket holding the two pieces together, when it is re-installed it is no longer "balanced" and causes a wobble and vibration, which could cause front main seal to start leaking.
I doubt he could hurt the bearings, but unless you noticed a knocking I doubt there is a bearing problem.

 

He called me up to the shop to show me it had a little wobble before putting the belt on then called me and said " when i put the belt on it is causing tension and hitting the crank sensor" so he said he's trying to figure a way to pull the sensor a little farther away with a fabricated bracket possibly. There was no knock but when accelerating it would stutter until i pressed down on the gas peddle further.

 

???
" when i put the belt on it is causing tension and hitting the crank sensor"

Makes no sense, belt is quite a ways away from crank sensor.
Crank sensor reads teeth on the Hub, and if hub was damaged then it would hit crank sensor regardless of belt being on or off.
And belt tension is not even close to enough pressure to cause hub to deflect.

What are the answers to the other question?

 

sounds like you need to get your money back, he did not fix anything!

 

Get your money back and get away from him, he doesn't have a clue what he is doing. RonD gave you more information in 10 seconds than you have from this yahoo.

 

So, rather than correct a faulty harmonic balancer (which he may have damaged as RonD pointed out using a wrong puller; he called you after he put the belt on (your words)), this mechanic wants to fabricate a bracket to get the crank sensor away from the wobbling harmonic balancer???

Your too deep into this mechanic now, so short of paying him and getting the truck finished elsewhere, I don't know how you can get this mechanic to make good on his repair.