#1
I recently got the MXL 550 and a551 microphone ensemble. I've been using a crappy old Peavey mic up until now and these are a HUGE step up so far. I figured i'll start double micing everything now that I have the ability to but I've never done it before.
Theorangeline.bandcamp.com is an example of how my old mic sounded and the musical sound I'm going for. Id just take the grill off the mic. I mic'd my drums by sticking the mic between my two toms and basically in the center of the entire kit. I never had an exact position when miking my amp but it was usually diagonal to the grill, id say 45 degree-ish and about a half inch/inch from the grill facing into the cone.
I don't know anything about miking drums. I know everyone usually says this is a preference-based topic but id like something to start off of. Can I use my large diaphragm (550) to double mic ky guitar and drums?
I had a lot more to ask but my memory sucks and drumsthis is a good start.
Gear:
Fender Telecaster w/ Dual Gibson Humbuckers
Ovation Celebrity Acoustic/Electric
Fender Frontman 212R
Band(s):
Old Too Young (Folk/Bluegrass/Punk)
The Orange Line (Stoner Metal/Punk/Alternative)
#2
Of course you can use it. Placement is going to be a big thing to think about. They're condenser mics and as such are far more sensitive than the dynamic mic you were probably using before. For drums what i like to do is have two matching condenser mics for over heads then at that point for added definition you can close mic each piece with a dynamic. Again for the guitar amp a dynamic (such as a Sure SM57) is used often but of course you can use the large condenser. I've found that using my condenser mic for vocals and acoustic guitar has been it's best use but like anything involving music ... experiment. You'll find something that works.

HomeRecording.com is a great resource. Lot's of knowledgeable people there.

Good luck.