Quoted from Archytas:
I literally did this last night (replaced some really dim LED's with bendy ones to light the inserts better). You can follow the manual but the easiest way I found to do it was the following:
1) Pull playfield up so it is resting on service rails.
2) Remove nut above playfield post on right, screw where the mini-playfield joins the ramp and there are 2 screws mounted to a metal plate on the lower left side above the pop bumpers (these are the worst 2, they are slightly underneath and in a bit of an awkward position). In total 4 things to remove.
3) Slide mini playfield forward - it should slide under the ramp and forward, if you are finding it is catching it is likely the wires from the lamp are behind the metal mounting bracket, move these round the bracket. As it slides forward feed the wires through the playfeld.
4) With the playfield out you should have enough slack with the wires to turn it sideways and get underneath, you will be greeted with a large cardboard protector mounted in place by 5 screws. Remove 2 of the screws that are close to the top which will allow you to bend the cardboard back enough to get to the lamps.
5) Replace lamps, there is also a flasher here so remember to do this as well.
6) Roughly mount playfield back in place, turn game on - test all lamps work, if they don't remove and adjust as required. (worst thing would be putting it all back and finding out 1 of them doesn't work!)
7) Remount into place. Enjoy new lamps!
The manual suggested unplugging the 4 connectors that attach to the mini-playfield but I found this wasn't necessary as I only had to get it out enough to replace the lamps and there was enough slack on the wires. If you do decide to do this MARK THEM - there are 2 with practically the same wiring and if you plug them in the wrong way round you will blow something up.
Nice, will follow these instructions to also install the mni-pf cliffy protectors I've been postponing for awhile!