Tricross Comp Chainset/BB (GXP) replacement

resentin Posts: 2
edited March 2013 in Road buying advice
Hi everyone,

I'm totally new to the forum, and quite a novice bicycle user/modder too so please be patient should I ask silly questions :)

I have just bought a second-hand Specialized TriCross Comp - model year 2010 (Shimano 105, double/10 speed). I could see that the chainrings were quite worn, but when serviced I was advised to replace BB (slightly worn) and chain as well (in worse state). I'd like to learn as much as possible about bike maintenance and be able to decide by myself what components adopt, even for the future, so I'll need some help and advice from the forums :) Thanks in advance to anyone who'll take the time to read and answer!

Now, the stock chainset/BB was a Truvativ Elita GXP 48/34 (BB shell width 68mm), though the chainrings were replaced with a 50/36 set.

I'd like to ask dozens of specific questions but the short version is:

What would you suggest?

More specifically:

shall I keep the same BB standard (GXP) or change?
Is it possible, say, put a GXP BB and a non-GXP crankset?
When you replace the chainrings, do you automatically get a whole new chainset (so with cranks)?
I see 46/38, 46/36, 50/34 and other options (funny enough, no 48/34) in online shops. Pro/Cons of these options (beyond the obvious difference in how they affect speed)?
I can't seem to find - in online shops and for a given chainset - different options for the shell width. Does it mean they would all fit? Need adapters?
Can I use any 10speed chain with any chainring I'll choose?
I was advised to look at KMC chain / cassette (yes I might replace that too!). Would they do with any choice I'll make for the other components?

If there's any specific product you'd advise, please attach the link to the shop selling it!

Note: I mainly use the bike for commuting in London (15 miles/day - often in the rain) but I do plan to do some medium-range touring on it as well. Also I may do some triathlon in the future, for the fun of it rather than with competitive hopes though. I'm obviously not a power cyclist and I'm rather on a budget but usually not lean towards the cheapest option anyway.

Many many thanks and sorry for the lengthy post!