Mine came off easy because they hardly used any thermal paste at the factory (doh!), but dont be afraid to pry them off. You have to get the "glue" off anyway, just dont bend the PC board or crack an edge when you do it. Try clamping the heat sink gently in a vice and use a tiny flat screwdriver and twist under the IC. Once unglued, you can bend the ICs away from the heatsink pretty far as you de-solder the pins. I would recommend you replace with the higher power chips (150s) also. They are identical in function but rated for higher power which might get you a few more years of life.
It sounds that the convergence adjustments should be re-touched.If you wish to get more details, check this site linked
below. Pull up older posts there. Check
the site with patience, as it has over 2350 posts now. All are related to electronic equipment
repair help. If you search the site in
Timeslide option, which can be selected from the drop down list at the top left
of the display window, it will be easy to locate the related post. You can also do a search by type in the
brand name to your device into its search box at the top right of display