New RL Owner in need of advice! Cover and wheels

Just got home with new 2009 RL RTL. Love the truck but using it for specific work needs. I am a land surveyor and need to secure (and keep dry) equipment in the bed. So far as I can tell, no way to lock tail gate! Guy at local truck add on place says retrax cover will not stay dry and folding cover is only other option for Honda. It does come off easy and no drilling which is good., but does not lock gate. Also same guy says after market truck (off road) wheels will not fit RL. I'd like to keep new tires, but change to black wheels. Any wise soles have advice for novice with Hondas?

Bakflip HD or G2 cover are as leak proof as it gets which by all accounts is very good. I have an HD, but it went on this summer and it went thru car washes and so far so good. Put in a Dyno lock and the tailgate locks up nice and tight. Mike

thanks, looks like my best option, with a Dynolock!