1. I do know people who drag their amp into stores when they go to buy an instrument if the store does not have the same models of heads and cabs, I once took my speakers to a stereo store to hook up to the different amps to choose which one sounded better. At any rate, any store that sold pro gear would be used to such sillyness, or would have an amp that matches yours, like I said, the range of bass amps is much smaller than for guitars, which itself is pretty limited (Fender, Marshall, Mesa, Orange)
2.
i would need to get a pick-guard custom made which was real expensive.I don't think so, you could either send a tracing of the size, or, just send them the original, because I would bet they have close to that size, or that exact size in stock. I'd write to them, unless you are real hot with the tools (and if you were, you'd own them,) having to do it a few times to get it right might well cost the same. They do nice work. It's the design/artwork on the guard that will tend to cost, a simple black or blood red guard cut would be pretty simple.
http://www.pickguards.com/