How hard is it to change engine mounts?

[svxsubaru1]

Iam not sure if there bad, but i think there going out, becasue my engine seems to rock around a decent amount and it has 128,000 on them. I was just wondering how hard is it to change the 2 under the engine is there a way so you dont need to take out the engine or use a engine hoist? I was thinking of ungrading to a STi mounts, but i rember redinging on this board that the plates cant be used or some thing, but i also read that the plates are spose to be diffrent for a more direct power dervilery? If i did the mounts should i use the plates if there are thicker?