Anyway I found an amp head in my shed. Its not guitar amp, but id sure as hell like to plug it in and see how it rolls. Its a Sansui "AU-55A". it has several inputs at the back, but i have no idea how to use them. Where do I plug the guitar in?

Phono 1 & 2, Aux, Tuner & Tape (switch). Aux can be used for CD, DVD, VCR, Headphone jack.
Pre-in Main-out RCA plugs on rear. This amp can be used as a pre-amp or power amplifier. The Pre-Amp, inputs and power supply are all shielded.

Where do I plug in the guitar, what adaptors will i need? I can figure out how to plug speakers in,

Jackson RR3 - BKP Painkiller/Warpig
Bugera 333XL 212
Pod Studio UX1
MXR Smart Gate
Hardwire CM-2
You want to put a guitar through that? I wouldnt tbh. But if you want to use it for a stereo that would make sense. for a CD player, i would go for the auxillary in's (AUX) if it has RCA outs on the CD player. Try tape in's if not.
hope it works