Misfire

Okay about a month or so ago, I bought a 99 Jeep
Cherokee 4.0 in-line 6. Ran great. Fixed the air had to put
a thermostat in(there wasn’t one). Anyways ran it a week
after that and noticed some problems. There was a touch
of green coloring in my oil so I was like okay, I’ll just go
ahead and change the head gasket, no biggie. Did that
myself all correctly and it ran for a total of 5 mins,
checked the oil and it was milky. So obviously it didn’t
seal. Had a shop come pick it. I was done messing with it.
Turned out the head was warped(I did that, whoops) also
it was cracked (that’s why it was barely greenish oil to
start with) I bought a brand new head. Costed me $500. I
easily threw $1000 at my Jeep and this shop. So I get it
back, I don’t even drive it 5 miles before it bogs down and
the oil light flashes on. I get mad but it stops. Next thing I
know I go another 30 miles and I have this misfire from
hell. Like it will barely stay running it is so bad. I put in all
new spark plugs and the wires are good and it is still
doing it. I am lost. It ran fine before the shop got a hold of
it.