I swapped out a 6000 hour tube with a 2000 hour blue on my 1252, but the electronics were already on the tube so the swap literally took 10 minutes. I don't thing it would be really difficult, but it looks like you need to be patient when removing the magnets etc... to get them to the new tube. I thought I saw a site describing the procedure but for the life of me can't remember where, maybe someone else does?
I don't think you'll have any problems working with one newer tube and two slightly older, but double check your green and red, I originally thought mine were clean, but they had a very slight wear, which actually is apparent when I go outside of the wear area (whites have just a tiny tint of red to them compared to outside the wear area). I couldn't see the wear on the tube themselves unless I looked at them while the pj was on projecting the warm up screen. Just something to keep in mind...
I don't think you'll have any problems working with one newer tube and two slightly older, but double check your green and red, I originally thought mine were clean, but they had a very slight wear, which actually is apparent when I go outside of the wear area (whites have just a tiny tint of red to them compared to outside the wear area). I couldn't see the wear on the tube themselves unless I looked at them while the pj was on projecting the warm up screen. Just something to keep in mind...