Right well firstly I didn't use a timer relay, purely because I didn't think I needed one.
The timer relay is fitted for numptys who can't remember to turn their screen off.
I trust you will not be one of those people if you can fit your own bloody screen in the first place!!
The screen needs to be fused at 30 amps per side and thus wired accordingly.
I use two 40 amp relays fused at 30 amps, switched by a single switch and supplied with power and earth from the bulkhead fitting (200 thing, 300 needs to pull from fusebox as suggested)
I honestly wouldn't bother with timer relay because you will never have it on that long anyway, the work very quickly!
If you do wish to use it, look on
Vehicle Wiring Products Ltd. Suppliers of auto electrical parts. as they have the pinouta for different types I relay iirc and that may help.
Failing that, the relay pinouts are likely to be identical to a normal relay, just this one switches off after some time. Is it 4 pin or 5 pin?
Is that of any assistance so far?