I have an 04' LSV and did the swap just a few weeks ago (hard tanks to bags)
Easiest way - buy two of these (one for each side) -
http://www.wakemakers.com/tankbuster...m-upgrade.html
.... after you remove the hard tanks this kit lets you use all the existing plumbing and pumps. You could "make" the kit cheaper yourself, but this setup makes it crazy easy. The whole process is like 60 mins for both sides to rip out the old and put in the new.
For bags, I went with 1100# Pro-X bags, they don't fill 100% though.... and for surfing, this is the way to go. For the VLX I would say either the 900# sumo bags or the 750s would work well if your main goal is wakeboarding.