To install new fork springs (not lowering springs) you do not have to tear the forks apart. Just take the top cap off pull out the spring, drain the oil, put in the new stuff, adjust your preload as req'd and hit the road.
To lower your forks either with the progressive lowering springs or with lowering blocks or with your own pieces or metal or pvc pipe, you have to disassemble the fork tubes from the lower leg. This involves removing the bolt on the very bottom of the lower leg. You can try an impact to get the bolt loose or you can fab your own tool tool to hold the damper rod while getting the same bolt loose.
You don't HAVE to replace the fork seals if they aren't already leaking and you are carefull during disassembly/reassembly. IMO you should though. May not be a bad idea to get the washer that goes on the bolt that holds the damper rod in too. Other than that, you should be fine. Some guys go for new dust seals but if yours are good, not torn, and still pliable and you don't gouge them during removal I would reuse them.
If you have tools, I would suggest you try it yourself. Take your time. Read up on it here, and check the manual.
Or, you could always just raise them up in the tripple trees. Thats the easy way out