It may be less expensive to do the electrical, but a gutting and drywall should more than offset any electrical savings. Switching from plaster to drywall often creates a fair number of framing or trim issues that would need to be addressed before the drywall could be done. It is also likely the owner would resist the replacement of the plaster if it's in good shape.
Working on the house may not be too bad, depending on it's age. If it's an old balloon framed house, it's pretty easy to fish.
One thing to look out for: most lath and plaster houses (at least the ones I'm familiar with) had all the trim put on before the plaster. If you are going to be pulling the baseboards, make sure you cut the plaster away from the board first. Also, check carefully for shims. A lot of times the baseboard is shimmed away from the studs, and the shims are taller than the baseboard. If you try to pull the board, the shim will usually come with it, along with a chunk of wall. With the baseboards out, going around the room should be easy.
Have fun.