I've got a MK1 1993 L plate mondeo, but AFAIK the speakers are about the
same...

the adaptor plate will allow any 6.5" speaker to fit into the door, you can
(if you want to cut the door...) fit 6x9 speakers, or you can replace the
originals with 6x8s (which tend to be a bit more expensive than normal
speakers because they're specially made).

The speakers tend to be around 20w, maybe as much as 30w, but I guess this
is a maximum rating rather than RMS.

Fitting the speakers is as simple as removing the door card (follow the
instructions in a Haynes guide) and unscrewing the old speakers, maybe
removing the plug that is on the end of the old wires and crimping on new
connections. Then just insert the new speakers into the plate, connect em up
and install the plate into the door. Easy. Have a good listen to different
brands of speakers if possible, everyone will say different speakers are
better than others...

good luck

PB