Big questions are:
- what are you hoping to achieve, why do you think that you need new wheels?
Are the wheels you have broken, bent? Aren't spinning smoothly?
Or are you hoping to go faster? First step on a journey of upgrades?
I don't get a lot of hits on a search on Shimano idex. Those I get are all from South America and usually lumped together with Shimano Tourney. Based on that (and the 7-speed is a clue too) I'd
guess that what you have is a fairly low-end bike.
For Shimano though, even low-end is usually perfectly serviceable. A bit clunky and chunky, but if kept reasonably clean and lubed fully acceptable for everyday riding.
Let's look at speed first - unless there's something wrong with your current wheels (bearings, spoke tension, trueness...) the amount of speed you'd gain from another set of wheels is most likely quite marginal. There are plenty of other things to work on before getting another wheelset becomes top priority.
There is probably some durability to gain by switching wheels. The rim you have is a single-wall, which tends to give poorer service than double-walled ones.
Not that it's in any way impossible to ride many happy miles on a single-wall.
Then there is compatibility. If your current rear wheel is of the freehub design, then it's possible to fit that cassette(+ a spacer) to a modern 8-9-10 speed freehub wheel to avoid messing with your chain and shifter.
But it might also be a freewheel design, in which case your options for a quality wheelset becomes somewhat more limited.
You are likely to encounter some issues with dropout width.
7-speed road is supposedly 126 mm, while 8-9-10 is 130 mm. Some simply muscle a new wheel in and call it done, other respace the new hub, yet some widen the frame and realign the dropouts before they're happy.
Biggest drawback I'd say to go hunting for a wallet-friendly wheelset is that they're all machine-built, and machine built(cheap) wheels are prone to spoke tension and bearing adjustment issues.
If you want to get good durability it's sensible to have spoke tension and bearing adjustment controlled by someone who knows what he's doing before starting to ride them - in which case you might have been equally well served by simply having your old wheels serviced instead.
If your current wheels haven't been heavily used and are still structurally sound(reasonably straight, no busted bearings), I'd say just get them serviced.
Tires degrade slowy over time anyhow, so new tires(particularly if the bike has been kept outside, in the sun) is probably a good idea regardless. Tubes usually do fine, not being exposed to sunlight and all that.
Last, I'd suggest that you head over to
www.sheldonbrown.com, where you can read up on all things bike related, and lose some of your noobity
