If you just want to swap lifters it's recommended to get the newer generation lifters that have larger oil wholes that don't get blocked and cause lifter tick. new lifters should be soaked in diesel and be sure to keep magnest away from them so you don't magnetize the ball valve inside.
SOHC or DOHC?
There is a guide here that does just the lifters not valve stem seals
This should get you going in the right direction. I beleive i used a tool that is a flat bar with a 45 angle to press the lever down so i could pull the rocker and lifter but it's been a while and i don't know where i got the tool. it's flat with a red plastic coated handle.
If you are doing lifters then look at doing the Valve Stem Seals also. Saves you burning oil and keeps the engine running cleaner.
official tool to compress springs is very expensive but there's a home made solution above. this works but takes some muscle and patience.
another solution that requires removing the cams
I'd say the lifters is pretty easy but valve stem seals requires a little more tools wise and time.