Hi Stirling and welcome to the MRF.
For the same reasons as yourself I moved over to N Gauge about a year ago and don't regret it for an instant. Not sure how 'ancient' you are but I'm rapidly aproaching OAP status so am certainly no Spring chicken myself.
Poliss has already hit the nail on the head regarding using the Kato track system with its built in point motors. I am, luckily, not under the same mobility constraints as yourself so am able to use Peco Code 55 trackwork with the points mounted beneath the boards.
As regards draw backs, one has to accept that the level of detail on locos and rolling stock cannot be the same as 00 for instance. Having said that, however, it is probably up to the same level as 00 was 10 years ago and is improving all the time.
The other thing to bear in mind is that N Gauge models are roughly only half the size of 00 which does tax the old eye-sight a little. This can be compensated for, to a certain extent, by investing in a good workbench light and magnifying glass.
The range of locos and rolling stock available in N Gauge is already quite extensive and, with the growing popularity of N Gauge, is increasing with every month that passes. Just look in any railwy mag and you will see plenty of reviews of new N Gauge items. Don't expect the prices to be half of 00 though. While a small tank loco can be picked up for under £30 and a King or Castle for about £75, which is about the same as 00, the newer, finer detailed locos such as the Ixion Manor will set you back £100 or so which is actually more than the equivalent 00 Gauge loco. This is, I believe, due to production runs being smaller but, as interest grows and more modellers move over to N Gauge, I would hope to see these prices coming down.
In case you are considering using DCC Control I can assure you that with the recent progress in DCC chip miniaturisation even the smallest 0-6-0 tank loco can now be DCC chipped so all of the benefits of DCC can now be enjoyed by us N Gaugers. The wiring is somewhat different to the traditional block sector approach but is, I believe, less complicated. You will, however, need to install a power bus beneath the baseboard and connect every piece of track and every point to that bus. The myth of just having 2 wires providing power to the entire layout is just that; a myth.
Hope this helps but if you have any more specific questions please feel free to come back to me. There are several of N Gaugers here at the MRF, though we are still in the minority, and we welcome all new-comers with open arms.