N20 and RPM "window" switch.

anyone using one of these?
http://store.summitracing.com/egnsearch.asp?Ntt=msd+rpm&N=4294849264+115+4294781653&Ntk=KeywordSearch

Is it as easy as it seems…?
I would really hate to mis-shift and break things…

K&S has one for $100, but I don’t know witch one…

any comments?.

edit: would I be better off switching the power to a Zex box, or
the TPS signal line?
edit2: It would be used on a DIS GM 2.4