1. The arc of the 52 chainring will obviously be significantly bigger than the arc of the 44. Assuming that you're using a front derailleur that was designed for use with a max 44 or 46 chainring, you're going to have trouble because the arc of the derailleur cage will be too small to match the chainring. You'll find that you have to install the derailleur way high up on the seat tube and it won't shift well.

Installing a front derailleur that's designed to work with a 52 chainring may not be so simple either. All of the road derailleurs that I'm aware of are downpull and require under the bottom bracket cable routing. If your bike was designed for use with a top pull derailleur, the cable stops will be in the wrong place.

The front Gripshift thing is a trick question. I'm not aware of any indexed 2 position front shifters. If such a thing does exist, it would be beyond the ability of a home mechanic to convert it to 3 position. If it isn't indexed it'll work fine.