Not hard at all.
I have recently resealed all of mine. Here is the procedure I used:1. Unscrew inside phillips screws that hold on the frame.(a portable drill with a phillips head works great!)2. Take off inside frame. (give it a good washing)3. With slow pressure push out the glass and frame (have an assistant or something to catch the frame from going in the drink, also it may need to slide fore or aft to remove it from the hole.)4. Clean off all the previous caulk and clean the surfaces with alcohol (not the drinking kind) to get a good bond.(THIS IS VERY IMPORTANT TO SEAL CORRECLY)5. Apply a bead of 4200 caulk to the cabin top or the frame. Don't use 5200 unless you "NEVER" want to take them off again.(I have also used a caulking putty that you can get from an RV dealer to caulk windows. It does not harden and is not as messy for us clutt'es!)6. Replace frame from outside, being careful not to smear the 4200 all over. Wipe up spills immediately.7. Replace inner frame and make sure it seats correctly. Tighten screws slowly and evenly around the port.After the 4200 sets up trim off excess with a knife. If you get a good bead all the way around the frame, you should have a leak proof seal. I did all of mine in about 2 hours. If it is cold you might want to put a heat source next to the port to soften the previous caulking.It is nice to have a boat where the water stays on the OUTSIDE!Good luck