No access underneath. You have to pull the cap off by removing the three top allen heads (the others are fake, open the cap and will see which ones). There is one allen head inside the cap too. After you lift off the locking cap, the easy part is over... Inside along the edge of the bezel are several very tiny allen head set-screws. After you remove all the little allens, you have to pull the bezel off the tank. This can be a bit of a pain! Keep working at it. It might feel like you are getting ready to pull the top of the tank off, but it does actually come out! Once you get that off, you'll be able to reach in from the top and get to the filter and pump assembly. Installation is the reverse. Things to be careful of... The green o-ring. I used a little petroleum jelly and worked it back in. Just be careful to not stretch or rip the o-ring. Also a bit of a PITA to put back in is the black rubber trim ring that you can see when the thing is all together. All in all it's not a hard job. You just have to take your time and not damage the 0-ring. It may even be a good idea to have on on hand before you start.

Oh... I just noticed your signature! Yes, the Hawaiians do like their spam and rice masubi (SP)!!!! There was a Wendy's near the Stadium on Oahu that sold the stuff along with Saimin... You sure don't see that on the Main Land!!!