Yes it would make a difference, even on XP - as an SSD is a faster drive, regardless of the OS.
You shouldn't have to make too many tweaks, though I've not played with one in XP, but essentially you'd just want to disable things like defrag from running on the SSD. You can make plenty of tweaks, most of them relate to avoiding unnecessary wear to the drive through avoiding writes, but IMO these are generally overkill because the drive will likely be obsolete before you wear it out. Otherwise most of the tweaks don't significantly improve performance, not noticeably in day to day use anyway.
One thing to look for is a drive with a manual TRIM tool (think of it as the equivalent of SSD defrag - but it actually cleans used parts of the drive instead). The OCZ, Crucial drives have a utility you can get called Wiper. The Intel drives should get a Toolbox utility in the not distant future.