Pump replacement problems

[c130jake]

Hi, I just got my 1hp Wisperflo and disconnected the very old and dying 1hp Pac-Fab pump.(>15 yo and rebuilt at least once) The new pump has 2" fittings and is about three inches taller than the old pump and I can't fit it to the old PacFab sand filter and slide valve connections without lifting it up about 3-5 inches and reducing it to 1.5 inch. (the filter and pump are mounted on a fiberglass unit with a circular stand for the filter) The plumbing is 1.5inch old sched 40 PVC. The return and multiport are 1.5 inch but the old filter has 2 inch fittings. The Heater is corroded and dead but not leaking yet and is also 1.5 inch plumbing. I think I need to just re-plumb the whole mess. The back flush slide valve is 2" and connected to the sand filter but has glued in 2-1.5 inch reducers. Should I bite the bullet and redo the whole mess? Are there any problems going from a 2 inch pump outlet to 1.5 inch lines. Do I make what I can 2 inch? If I get a new heater, are they usually 1.5 or two inch plumbing? Are there any good do-it-yourself web sites for replumbing a pool? The sand filter is an old 2.7 square footer but seemed to work well. Just put new sand in for this year.
I will try to attach a pic to show you what I mean. There is also an old inline chlorinator that could go away and my new SWG.....I need to get the water moving again...