If it's just one wall, then I would allow four/five days for a complete novice depending on the size of the wall.
* Taking the old tiles down shouldn't take long. Wear goggles and gloves since the tile chips are bloody sharp!
* First day work out where you tiles will be placed. Try and ensure that you don't end up with slivers of tiles. Work out the center of the wall and measure from that datum to the corners and decide if you need to have the grout line on that datum or the center of a tile so that you have the largest bit of tile when you reach the corner. Don't forget to take into account the grout of 2mm. Make sure you also take into account door height, window height (if you're not tiling up to the ceiling), where the toilet is, the basin, the bath edge, anything else. You can cheat by laying a piece of wood on the floor and placing the tiles and tile spacers on the floor alongside it and make marks on the wood and then transfer them to the wall. Whatever you do take a long time over this!
* Then prepare the walls. Remove any wallpaper if you're tiling a largeer area than before. Remove as much old adhesive as possible to get a relatively flat surface to tile to, you might have to sand the walls. Sugar soap any other part of the walls. Don't use PVA unless the adhesive instructions say you have to. This might take up to a day to do depending on the state of the walls and if any plaster comes off with the old tiles!
* On the second day you can start tiling all the whole tiles. If there is a gap between a tile and the floor/bath/basin/toilet then place a piece of wood on the wall to hold up the tiles while the adhesive sets.
* Depending on the size of the wall, start cutting tiles and doing all the fiddly bits on the 3rd day. This may take more than a day if you have lots of cutting and expect lots of broken tiles
. An electric tile cutter may help.
* Next day, do the grouting. Read the instructions, some grouts/adhesives need 72hours to allow them to really dry out.
* Final day and the shortest, re-seal around the bath and basin, stand back and admire your handiwork.
HTH