May be you should get the cycle modded like the one you've in your avatar
Sry @2strokerama, couldn't help commenting. Sry if it hurts!!!

not a bad idea at all...my old 2t is more or less spare parts now anyway......maybe I can score some chicks with that new dejain bike.

Oh shit....it looks like a YBX tank....

yes yes, enough making fun of the bikecycle....

can some one help me with what I asked?

That is a Malay RXZ 6speed body kit.

For the budget you have it will be a bit difficult to get parts of TREK quality. However you can get Alloy rims complete with disc brakes and tyres. Why dont you go for a Raleigh MTB [forgot the name] it comes with Shimano gears, front suspension, alloy rims and a front disc for around 7k.
Try Bikeszone.com for mod tips.

check this out.

BikesZone - Cycling • View topic - Raleigh Bicycles

The other one is the Raleigh elevation 2.0 and 3.0 . Available at Hypercity stores.

@yamdoot: Thanks for taking the trouble man. Well, as I mentioned before, current plan is give my topgear a partial overhaul.....basic changes on a necessity basis for now. So, in keeping the old frame and forks, Ive ruled out suspension but I want a new set of wheels i.e rims and tyres(I'll stick with stock rim-brakes for now), a good handlebar, seat, chain and gearing...not overkill, but enough for a comfortable intra-city dash and\or occasional offroading. Id rather not compromise on quality (affordable within my budget) and whatever I can save on new frame and forks, Id like to spend on other parts.....so Im hesitant on a new bike if I can build a good enough bike from the old bones.

I'll check out those cycles(and others) if I can find some suitable parts. In the meantime, if its not too much trouble, can you suggest how I can break down my expenditure on the parts I want in the best possible way?

I had the same needs and went ahead.
My cycle which was stored away in my room for 16years is now back in action.
Its a Hercules MTB.
Perfect running condition, but I had to change some stuff.
I got the seat changed into a imported gel foam type so no more soreness.
Tubes changed, wanting to change the tyre too.
Added a water bottle holder (Btwin)
Water bottle (Puma)
Cyclometer (Cateye)
Headlight and rear blinker (Cateye)

Its a good looking bike now and do daily rides
But I am not able to do longer rides because the frame is small compared to the actual size for my height on imported cycles.
They cost around 1.5 Lakhs which I was not ready for so I am happy with short rides.

I would like to add gear system but I wonder whether it is possible.

Yes ,There are gear kits available from Shimano and other brands. around 1.5KINR- #KINR

I did it in my brothers Hercules Devil long time ago

Absolutely no chance it will be anywhere near 'Trek quality'

Why?

Simple - your frame is not even in the same league. Sorry to sound harsh but its a realistic critique. However, if it is a sentimental attachment, then go ahead, but its a waste of money to put quality kit on that frame. Cost - decent drivetrain will set you back 2k+. Decent gearing will cost you at least 5lk. Decent wheels will probably cost you at least 5k. Tyres alone cost about 2k each these days, depending on the quality. I haven't even mentioned a brakeset in this case. I don't even know if your Hercules Top Gear fork will be compatible with new wheels and brakes. You need to check that.

My advice - put local stuff on the bike for cheap if you are sentimental about it. Then use the rest of the money and add a bit more to buy a decent entry-level bike i.e. the BTwin Rockrider 5.0 from Decathlon.