blkZ28spt

I have a converter going in next month and obviously want to keep an eye on the tranny temps so I will be purchasing autometer's pillar mount and an electric transmission temperature gauge........if I get the one that holds two or three gauges what other gauges should I to get?? I have a 98 so my stock gauges should be trust worthy (volt meter, oil pressure, coolant temp), correct? Is there anything else? All I can think of is oil temperature. I have done some searching and came across a wiring diagram for the back of the radio head unit that should come in handy on install but I have never done anything like this before if I just follow instructions will I be okay? I also read that people used some sort of a T to wire the sending unit for the trans gauge into a wire leaving the transmission....what is that exactly/where can I get one? Any weird tool or something I might need for the wiring? THANKS!